Oil, Lubricants and Gasoline
QUESTIONS
  1. After an oil change, I noticed 5W20 was installed in my vehicle that calls for 5W30 motor oil. Is this a problem?
  2. After having my oil changed I noticed a spot under my vehicle. It seems to be coming from the drain plug, but I checked and it is tight. Why would a tight drain plug leak?
  3. Are high performance air filters, that use oil on the element, worth the money?
  4. Can grease fittings be added to my suspension that does not have them?
  5. Can I increase fuel mileage by driving slower?
  6. Can I increase fuel mileage without replacing my vehicle?
  7. Can I safely extend the oil change interval on my vehicle if I use synthetic oil?
  8. Can I substitute 10W30 oil for 5W30 oil?
  9. Can I use automatic transmission fluid in my power steering or must I use power steering fluid?
  10. Can I use regular 5W30 instead of dexos in my 2011 and up GM vehicle?
  11. Do diesel vehicles get better mileage than gasoline powered vehicles?
  12. Do high performance air filters increase fuel mileage?
  13. Do I have to buy dexos oil from a GM dealership?
  14. Do you recommend any engine oil additives?
  15. Does engine oil evaporate?
  16. Does mixing regular oil with synthetic oil damage my engine?
  17. Does Summer driving require thicker engine oil?
  18. Does the octane rating of gasoline have anything to do with quality? Can an engine designed for 87 octane benefit from 89 or 93 octane fuel?
  19. How do I accurately check my fuel economy?
  20. How often should I change my oil?
  21. I accidentally put 93 octane fuel in my vehicle that calls for 87.
  22. I do my own oil changes. A friend said I should fill the filter with oil before installing it, to help get oil into the engine faster?
  23. I drive about 500 miles a week, mostly highway. How often should I change my oil?
  24. I have a Buick with 29,400 miles. It is making a buzzing sound on acceleration and driving. When you slow and stop, the buzzing slows and stops. If it helps, the buzzing started after I had an oil change and air filter change last week.
  25. I have a clear, oily fluid under my vehicle, what could it be?
  26. I have always used a certain name brand oil in my engine. The last time I was in the parts store the salesperson told me they have a less expensive private label oil, made by the same company. Should I consider switching to the less expensive oil?
  27. I have just purchased a new vehicle and wonder when I should do the first oil change? I have heard several opinions and would like yours if you don’t mind?
  28. I have some old Mercon transmission fluid and was wondering if it will work in my truck that calls for Mercon-V?
  29. I notice the abbreviation API followed by SN on my oil, what does this mean?
  30. I recently bought a new vehicle that calls for 5W20 motor oil. That seems awful thin in this hot climate. Would 5W30 be better?
  31. I saw an advertisement for pills you can add to your gasoline to increase mileage. Do these really save gas?
  32. I was told by my mechanic that I was greasing the suspension on my car too much. I usually grease all the fitting at every oil change (3000 miles). Is this too much?
  33. I was told the automatic transmission fluid in my Honda is not the same as other cars, is this true?
  34. Is adding a can of fuel injector cleaner to my vehicle, now and then, a good idea, or is it just another scam?
  35. Is brake fluid the same as power steering fluid?
  36. Is conventional engine oil recommended for vehicles used in hot regions?
  37. Is it bad to put non-recommended oil in your car?
  38. Is Mobil1 5W30 approved for use in 2011 and up General Motors vehicles that call for dexos?
  39. Is the oil filter sold by the maker of my vehicle the best one to use?
  40. Is there a way to look at a fuel filter and tell if it needs to be replaced?
  41. It is time to pack the wheel bearings on my truck. Is there any problem changing to synthetic grease when packing bearings?
  42. My car calls for 5W30 oil and this seems very thin for the hot climate I live in. Would 10W30 be a better choice?
  43. My car has started to use oil, should I switch to a heavier viscosity?
  44. My car manual recommends I use 5W30 oil, would you still use the recommended type even when the car has high kilometers and is over ten years old?
  45. My Chevrolet calls for dexos1 oil, is this the same as viscosity?
  46. My owners manual says I should change my oil every 5 month or 5,000 miles. I drive about 2,000 miles every five months. I do not understand why I should change the oil with only 2,000 miles of usage. Does oil go bad in five months time?
  47. My power steering fluid was low and the pump was making noise. I added fluid and the noise went away, but after I turned off the engine, the fluid came pouring out the reservoir opening.
  48. My truck is equipped to run on flex-fuel. If I switch to E-85 will my fuel mileage go up, down or stay the same?
  49. My vehicle calls for 0W20 motor oil which seems awful thin. An internet forum makes a compelling argument that 5W30 would provide much better lubrication.
  50. My vehicle calls for premium 93 octane fuel. Can I substitute regular fuel?
  51. My vehicle has 160,000 miles and the U-joints have started to squeak. There are no grease fittings in the present joints. Should I replace the joint with the type that has a grease fitting?
  52. My vehicle has about 50,000 miles and I am interested in switching to synthetic oil.
  53. My vehicle has been stored for about a year and I am concerned about the gasoline in it. Should I add fuel stabilizer before I try to start it?
  54. My vehicle has never used oil until I recently had an oil change. I have had to add oil twice (1000 miles) since the change. What could have happened with just an oil change?
  55. My vehicle is not driven every day and I only put about 6,000 mile a year on it, mostly very short trips. Can I change my oil once a year?
  56. My vehicle list a specific automatic transmission fluid, is this just marketing or should I use only the recommended fluid?
  57. My vehicle manufacturer says that the automatic transmission fluid does not need replacement, unless I tow a lot. I do not tow, it has 155K miles and has never been changed. Change or leave it alone?
  58. My vehicle says synthetic oil should be used. Is this the same as 5W30?
  59. Recently an oil change shop told me my engine was full of sludge and should be flushed. I have no symptoms, should I be concerned?
  60. Should I have the fuel injectors on my car cleaned to improve my gasoline mileage?
  61. Should I switch to synthetic Oil?
  62. Should I try to find fuel without ethanol for my vehicle?
  63. Should I use high-mileage formula oil in my older vehicles?
  64. Should power steering fluid ever be replaced?
  65. Should the lubricant in the rear differential be replaced?
  66. Since new, I have used synthetic oil in my vehicle. On the last oil change the dealership accidentally put regular oil in it. I have heard this will damage my engine.
  67. The fuel mileage on my Toyota has really dropped lately. I’m down about eight miles per gallon from the mileage I was previously getting. The check engine light is not on and I see no apparent reasons for the decrease.
  68. The fuel mileage on my vehicle is lower when my wife drives it than when I drive it. How can this be?
  69. The owner's manual of my 2011 General Motors car says use only dexos1 oil. Is this a new type of oil?
  70. What do the numbers and letter like 10W30 mean with regards to oil?
  71. What does the word weight mean in relation to engine oil, like five weight oil?
  72. What happens if I over fill my engine oil?
  73. What is the best engine oil?
  74. What is the difference in 5W30 and synthetic oil?
  75. What will happen if you put E-85 fuel into a standard gas motor?
  76. Where can I dispose of engine oil?
  77. Where does the engine oil go when the dipstick is low?
  78. Which engine oil should I use?
  79. Why did Ford revise the specification on the engine oil in many of their V-8 engines from 5W30 to 5W20?
  80. Why do mechanics wipe off the oil dipstick and then put it back in before taking an oil level reading?
  81. Why does driving faster burn more gas?
  82. Why is synthetic oil not recommended for older engines?
  83. Why would engine oil turn milky brown in color?
  84. Will it hurt my engine to temporarily mix petroleum with synthetic oil?
ANSWERS
  1. After an oil change, I noticed 5W20 was installed in my vehicle that calls for 5W30 motor oil. Is this a problem?

    Where 5W30 is specified, only it should be used. The 20 in 5W20 indicates the SAE rating for hot viscosity. A 20 weight oil is lower in viscosity than the 30 weight oil specified. This means the oil is much thinner at 100 degrees Celsius, operating temperature for most engines. The proper oil should be installed before the vehicle is driven.

    A possible exception would be certain Ford products. Ford has revised the specification on many of their engines. The original specification was 5W30 but has been revised to 5W20. If this is the case, using 5W20 is perfectly acceptable. Ask the oil change facility if there is a reason they installed 5W20 and if your Ford vehicle falls into the category where it is recommended.

    A more detailed article on oil viscosity is in our Detailed Auto Topics section under Oil Viscosity.

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  2. After having my oil changed I noticed a spot under my vehicle. It seems to be coming from the drain plug, but I checked and it is tight. Why would a tight drain plug leak?

    The threads on a drain plug do not seal. Only pipe threads that are tapered can form a liquid tight seal. Instead, most oil pan drain plugs have a seal washer or O-ring. The seal is under the head of the drain plug and is the actual seal. If the O-ring is worn or damaged or if the seal is crushed or omitted, the oil drain plug will leak.

    A more detailed article, on oil drain plugs, is in our Detailed Auto Topics section under Stripped Oil Pans and Plugs.

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  3. Are high performance air filters, that use oil on the element, worth the money?

    The original equipment filter, supplied by the OEM manufacturer is usually the best overall choice. Air filters do NOT increase fuel mileage. From that respect, the high performance filters are no better. Other problems include time required to maintain (clean and oil) the high performance models. If oil gets on an air flow meter it can quickly be ruined. We remove so called performance filters frequently after replacing air flow meters.

    For more information, please see our Detailed Topic When Should Air Filters Be Replaced.


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  4. Can grease fittings be added to my suspension that does not have them?

    Possibly, but I would advise against it. Most modern suspension components are designed to not have grease added. This is for good reason. One of the leading causes of failure in suspension and steering components was improper lubrication. Excessive lubrication ruptured the protective seals, causing rapid failure. Perhaps worse, the excessive grease sometimes found its way onto braking components, ruining them as well.

    Severely over greased tie rod causing contamination of disk brake
    Modern components, without grease fittings are pre-lubricated with synthetic grease. These last far longer and give far less problems than the older components that could be greased.

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  5. Can I increase fuel mileage by driving slower?

    Driving slower and accelerating easier will make a major increase in fuel mileage on most vehicles.

    For more information, please see our Detailed Topic, Driving Tips for Better Fuel Mileage.


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  6. Can I increase fuel mileage without replacing my vehicle?

    Fuel mileage can almost always be improved some. The first thing is to make certain the engine is running the best it can. Address any “check engine” light immediately and have the tune of the engine checked about every 30,000 miles.

    Engine temperature has a drastic affect of fuel mileage. If the vehicle has a gauge, be certain it is all the way into the normal range. An engine running below temperature will waste a lot of fuel. Tire pressure and wheel alignment also affect fuel usage, but to a much smaller extent. Tires should be inflated to about 10% under the tire makers maximum for best fuel mileage.

    Driving habits have the largest affect on fuel mileage. Fast starts and stops waste a lot of fuel. Also driving at higher speed requires a lot more fuel to travel the same distance at lower speeds. Driving 68 mph rather than 72 mph may save 3-5 miles per gallon.

    A more detailed article on increasing fuel mileage is in our Detailed Auto Topics section under Saving Gasoline, Saving Money.

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  7. Can I safely extend the oil change interval on my vehicle if I use synthetic oil?

    My answer would be no, for the following reasons. Synthetic oil is tougher and lubricates better than conventional oil. From a standpoint of breakdown, it is capable of protecting the engine for a longer period. It also cleans the engine better than conventional oil. Synthetic oil gets as contaminated and perhaps more so than non-synthetic oil.

    One important function of engine oil is to remove and suspend contaminates that enter the engine. Solid contaminates, above a certain size, are removed by the oil filter. Liquid contaminates and smaller solids [40 microns or less] can pass through the filter. These contaminates may cause sludge, wear and corrode engine surfaces. They are removed when the oil is properly changed.

    Synthetic oil offers many benefits, but extended oil change intervals do not represent overall lowest cost, in my experience.

    A more detail article on change interval is in our Detailed Auto Topics section under The Sad Truth.

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  8. Can I substitute 10W30 oil for 5W30 oil?

    Substituting oil viscosity is inadvisable. In an engine that calls for 5W30, there would be no benefit in switching to 10W30. Both oils are equivalent to 30 weight at 100 degrees Celsius. The 5W30 simply provides better flow at low temperature than 10W30 with equal protection at operating temperature.

    A more detailed article on oil viscosity is in our Detailed Auto Topics section under Oil Viscosity.

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  9. Can I use automatic transmission fluid in my power steering or must I use power steering fluid?

    Some manufacturers recommend automatic transmission fluid or ATF and other manufacturers recommend differing types of power steering specific fluids. Ford, Chrysler and Toyota have recommended ATF in several models. GM normally recommends power steering fluid. Honda and some others have a specific fluid they recommend. I always install what the manufacturer recommends. Even the most expensive specialty fluids are very inexpensive, when compared to the cost of a hydraulic failure in a power steering system.
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  10. Can I use regular 5W30 instead of dexos in my 2011 and up GM vehicle?

    Dexos is not an oil. Dexos is an oil specification issued by General Motors for their vehicles. Standard 5W30 will not likely meet this specification and can cause engine problems not covered by the GM warranty. Most oils that meet and exceed dexos, like Mobil One, will be synthetic or at least synthetic blends. The safest bet is to use a product approved under dexos unless you can be sure it meets or exceeds the specifications.

    For more information, please read General Motors dexos oil in our Detailed Topics Section.


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  11. Do diesel vehicles get better mileage than gasoline powered vehicles?

    All other factors equal, diesel will provide better fuel mileage than gasoline. This is because diesel fuel contains more oil [energy] per gallon. Diesel engines also run at much higher compression ratios. With more compression the fuel/air mixture will explode more violently, releasing more energy.
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  12. Do high performance air filters increase fuel mileage?

    Air filters do not increase fuel mileage. Even a badly clogged filter will NOT lower fuel mileage. As the air flow is decreased the fuel that is added is also decreased and fuel mileage will remain constant. This is not to say air filters should not be changed. A dirty or clogged filter may affect performance and may get sucked into the air box, allowing unfiltered air to enter the engine.

    A more detailed article on increasing fuel mileage is in our Detailed Auto Topics section under Saving Gasoline, Saving Money.

    For more information, please see our Detailed Topic When Should Air Filters Be Replaced.


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  13. Do I have to buy dexos oil from a GM dealership?

    The dexos license is sold by General Motors to oil producers. Any manufacturer that buys their license can provide approved oil. GM enforces this by stating it may void the warranty if licensed oil is not used. Not all oil producers are willing to pay GM for the license. Best is to look for the dexos logo or contact the oil company to see if they are licensed.

    For more information, please read General Motors dexos oil in our Detailed Topics Section.


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  14. Do you recommend any engine oil additives?

    I have seen no evidence that oil-additives offer any benefits over quality oil without additives. No vehicle manufacturer or oil company that I am aware of recommend their use and I agree. The highest quality oil available (API classification) should be used and it should be replaced frequently. If extra protection is desired, consider changing to synthetic oil. Check Should I switch to synthetic oil, for more details.
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  15. Does engine oil evaporate?

    In general, almost no oil is lost due to evaporation. There are certain volatile components that can be lost if left exposed to air over time. In an automobile engine this is almost imperceptible and will not account for a significant amount of oil.
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  16. Does mixing regular oil with synthetic oil damage my engine?

    Different brands of oil, whether conventional or synthetic, use different additive packages. For this reason, I feel it is better to stay with a single brand of oil. As long as the additive packages are compatible, mixing conventional and synthetic oils should cause no damage.

    A more detailed article on synthetic oil is in our Detailed Auto Topics section under Should I Use Regular Or Synthetic Oil.

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  17. Does Summer driving require thicker engine oil?

    Summer temperatures are not a consideration as all engines operate far in excess of ambient temperature. To an engine that operates near 100 degrees Celsius, there is no difference in a mild Spring or the hottest summer day. Cold Temperatures are much more of a concern, as the engine must be lubricated on startup. Thicker oil does not flow well at low temperature.

    This is why manufacturers specify multi-viscosity oil, capable of handling a wide range of conditions. For instance, 5W20 has the same flow characteristics as five-weight oil at zero degrees Celsius and the protection of 20-weight oil at 100 degrees Celsius.

    A more detailed article on oil viscosity is in our Detailed Auto Topics section under Oil Viscosity.

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  18. Does the octane rating of gasoline have anything to do with quality? Can an engine designed for 87 octane benefit from 89 or 93 octane fuel?

    Octane rating and the quality of the gasoline should have no correlation. Many modern vehicles will give better performance and sometimes better economy with a higher octane fuel. Higher octane allows engine timing to be run at a slightly higher rate. Whether the additional cost of higher octane fuel is justifiable would take some experimentation.
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  19. How do I accurately check my fuel economy?

    The most accurate way is on a long trip where you will use multiple tanks of fuel. Start with a full tank and record beginning odometer reading. When refilling, fill the tank until the first time the nozzle cuts off. Record the odometer reading and the number of gallons used. Repeat this on each fill up.

    When finished again fill the tank until the first cut off and again record the miles. Now with a little math you can record total mileage. Simply subtract beginning miles from ending miles for total miles traveled. Then add total gallons used. Divide total miles by total gallons to get miles per gallon.

    The more miles driven the more accurate the calculation, as this will average minute differences in fill amounts. By recording driving conditions for each segment [mountains, high speed, cold weather, etc.] you may also determine the affect each type driving has on your vehicle mileage.

    For information on increasing fuel mileage, please see our Detailed Topic, Driving Tips for Better Fuel Mileage.


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  20. How often should I change my oil?

    The answer depends on the manner in which the vehicle is operated. Most manufacturers widely advertise very long [7,000 to 15,000 mile] intervals. They also state under severe conditions oil should be changed much more frequently.

    The conditions that constitute severe service may surprise many people. For instance, if the average drive is less than ten miles, the vehicle may be considered severe service. Stop and go traffic may be considered severe service. Sitting at traffic lights with the engine idling and vehicles that do not get driven every day, are also very hard on engine oil.

    Driving every day, for long distances, is very easy on oil, and longer intervals may be okay. If most driving is short trips and stop and go, my experience is that 3,000 mile changes are much more cost effective, considering the possible consequences.

    A more detail article on change interval is in our Detailed Auto Topics section under The Sad Truth.

    For more information on changing oil, please see our Detailed Topic How to Change Your Motor Oil.


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  21. I accidentally put 93 octane fuel in my vehicle that calls for 87.

    If the engine does not require the higher octane fuel, it simply will not be used. This should have no real affect on the engine. Using 87 octane where 93 octane is required is a different matter. This can lead to pre-ignition [valve clatter, ping] and quickly cause serious damage.

    For more information on valve clatter see our article Valve Clatter, Spark Knock, Pinging and Pre-ignition.

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  22. I do my own oil changes. A friend said I should fill the filter with oil before installing it, to help get oil into the engine faster?

    The danger is, any debris that enters the filter, through the outlet hole, will not be filtered and will go straight into the engine. Oil, even from a sealed container is not always perfectly clean. Best is to use an original equipment filter, quality oil and let the oil flow through the filter, by filling the crankcase.

    For more information on changing oil, please see our Detailed Topic How to Change Your Motor Oil.


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  23. I drive about 500 miles a week, mostly highway. How often should I change my oil?

    Highway driving, for longer distances at a time, is very near ideal conditions for oil. The engine is at full operating temperature and running at peak efficiency under this type use. Under these conditions longer change intervals are possible and any quality oil will work just fine. Three-month change intervals should be adequate under these conditions.

    A more detail article on change interval is in our Detailed Auto Topics section under The Sad Truth.

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  24. I have a Buick with 29,400 miles. It is making a buzzing sound on acceleration and driving. When you slow and stop, the buzzing slows and stops. If it helps, the buzzing started after I had an oil change and air filter change last week.

    Check to see if the noise can be duplicated with the vehicle sitting still and in park. If the noise is still there, I would first suspect it is related to the filter replacements. If not the noise is more likely related to the suspension or drive line.

    If the noise can be duplicated sitting still, it could be the air filter housing was improperly installed and is now rubbing on an engine drive pulley. A defective air filter can also cause a similar noise.

    First check the installation of the air filter and see if it is a genuine Delco replacement. If not, temporarily remove the air filter and see if the noise goes away.

    If it does not, check the oil filter and again see if it is a genuine Delco replacement. A restricted oil filter can cause the oil pump to buzz as the oil bypasses the filter.

    Some times quick-lubes, franchises and even some dealerships and independent shops use inexpensive aftermarket parts that can cause such issues. AGCO recommends and installs only genuine Delco filters on GM vehicles.

    We also install only genuine OEM replacement filters on any make we service. For instance, Toyota filters on Toyota, Honda filters on Honda, Motorcraft filters on Ford, etc.

    A more detail article, on oil filters, is in our Detailed Auto Topics section under All About Oil Filters.

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  25. I have a clear, oily fluid under my vehicle, what could it be?

    Many fluids used in automobiles have dye added for identification. There are also several that are clear. Power steering fluid is one of the more common clear fluids. There is sometimes also a noise when turning the steering wheel with a power steering leak. Brake fluid also appears clear, though it is actually slightly amber in color. Brake fluid leaks often appear at the wheel area or under the master cylinder. A lower than normal brake pedal and a brake warning light may also be present.

    Engine oil that is very clean may also appear to be clear. This is common after an oil change and can indicate a leaking oil filter or drain plug. Oil that is spilled on the engine, may appear as a leak, sometimes days later. Other possible sources are a leaking shock absorber, rear differential fluid and leaking air conditioner refrigerant oil.

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  26. I have always used a certain name brand oil in my engine. The last time I was in the parts store the salesperson told me they have a less expensive private label oil, made by the same company. Should I consider switching to the less expensive oil?

    Checking with the manufacturer of the oil you mentioned, I was told the private label is manufactured by the brand name company. It was stated they are similar but not the same product. Further it was stated the name brand exceeded API (American Petroleum Institute) standards and the private label meets them.

    AGCO sells nothing but brand name lubricating oils, selected for their lubricating characteristics. I would use nothing else in my personal vehicles.

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  27. I have just purchased a new vehicle and wonder when I should do the first oil change? I have heard several opinions and would like yours if you don’t mind?

    If maximum engine life is the primary concern, I would do the first oil change at 500 miles. I would then change again at 1,500 miles and every 3,000 miles thereafter. When an engine is manufactured there may be a good deal of debris that escapes the cleaning process. These frequent initial changes help address this issue.

    Changing the oil and filter on a new engine at 500 miles, allows much of this debris to be removed early on. The second change is for additional safety and optimum results. It is also important to use a high quality oil filter capable of removing at least a 40 micron particle. The original equipment manufacturer’s filter will always meet this standard and is what we install and recommend.

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  28. I have some old Mercon transmission fluid and was wondering if it will work in my truck that calls for Mercon-V?

    Mercon is a brand name used by Ford for their transmission fluids. The original Mercon fluid is a conventional fluid, roughly equivalent to Dexron. Mercon-V is a synthetic based fluid. Mercon-V could be used in place of Mercon, but not the other way around. Mercon does not meet the specifications of Mercon-V and should not be substituted.
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  29. I notice the abbreviation API followed by SN on my oil, what does this mean?

    API stands for the American Petroleum Institute, one group that classifies oil. The two letter rating starting in the 1920's with SA, “S” meaning Service or passenger car and light trucks. The SA rating was plain mineral oil without any additives. As oils improve so do there classification. SA became SB and then SC and so on. SL came into being around 2001 and early in 2005 SM was introduced. Offered in late 2010 the SN rating is the latest standard of the API.
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  30. I recently bought a new vehicle that calls for 5W20 motor oil. That seems awful thin in this hot climate. Would 5W30 be better?

    Modern engines use oil for many things other than just lubrication. Engine oil often operates variable valve timing, displacement on demand and has an affect on catalytic converter life. The best oil is that specified by the manufacturer, 5W20 in this case. If lubrication is a concern you may consider switching to a synthetic oil.

    A more detailed article on oil viscosity is in our Detailed Auto Topics section under Oil Viscosity.

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  31. I saw an advertisement for pills you can add to your gasoline to increase mileage. Do these really save gas?

    I have seen no evidence that such products do any good at all and they may even be harmful to your vehicle.

    See our Detailed Topic article Wasting Money and Not Saving Fuel for far more details.

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  32. I was told by my mechanic that I was greasing the suspension on my car too much. I usually grease all the fitting at every oil change (3000 miles). Is this too much?

    Over greasing can be a problem. The additional grease tends to accumulate and attract dirt. This dirt often ends inside the part if fittings are not cleaned properly before lubricating. Excess grease may also rupture the seals on parts allowing severe contamination and allowing grease to find its way onto brake components.

    Proper lubrication involves cleaning the fitting and then stopping before the bellows, on the part, starts expanding. Synthetic grease is very durable, once every third oil change is normally sufficient.

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  33. I was told the automatic transmission fluid in my Honda is not the same as other cars, is this true?

    Honda vehicles should use only Honda brand ATF-Z1 or equivalent automatic transmission fluid. Honda ATF-Z1 fluid is a Dexron base but contains additive and friction modifiers required by the Honda transmission.
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  34. Is adding a can of fuel injector cleaner to my vehicle, now and then, a good idea, or is it just another scam?

    I advise against routine use of injector cleaner in fuel systems. It is not necessary, as injectors are self-cleaning. Repeated doses of high detergent may also erode the protective coating on the injector tips. With flex-fuel vehicles it may also adversely affect the flex-fuel sensor. It may also damage the fuel tank, as most tanks are now made of a plastic material.

    When injectors become clogged badly enough to require cleaning [rare] we use a system that bypasses the fuel system and feeds the chemical directly into the fuel rails. This avoids running cleaner through the tank, fuel pump, sensors and lines.

    Please see our Detailed Topic Fuel Injection and Wallet Flushing for more information.


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  35. Is brake fluid the same as power steering fluid?

    Brake and power steering fluids are totally different and must never be substituted. Brake fluid is generally an alcohol based fluid. Power steering fluid is generally a petroleum based fluid. Petroleum will rapidly destroy the seals and rubber components of a brake system. Brake fluid on the other hand, will not lubricate the power steering system and will quickly promote corrosion in the system.
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  36. Is conventional engine oil recommended for vehicles used in hot regions?

    Ambient temperature is not much of a factor in oil selection. Engines routinely operate above 200 degrees Fahrenheit, far greater than any ambient temperature. If there are concerns, synthetic oils resist heat better than conventional oils. Unless synthetic oil is otherwise recommended for the engine by the manufacturer, conventional oil will hold up in hot regions.

    It should also be noted if high ambient temperature causes the engine to run hotter, it may be considered severe conditions. Severe conditions call for more frequent oil change intervals.

    A more detailed article on synthetic oil is in our Detailed Auto Topics section under Should I Use Regular Or Synthetic Oil.


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  37. Is it bad to put non-recommended oil in your car?

    Yes, in modern vehicles, engine oil does far more than just lubricate the engine. There are variable cam timing mechanisms, hydraulic tensioners, displacement on demand and several other things that use engine oil. There are also many other factors, such as the affect of crankcase oil on catalytic converters, cold start lubrication, fuel mileage and so on to consider. Manufacturer’s take these and many other factors into account when specifying the proper engine oil. The vehicle manufacturer’s recommendation should be followed for best results.
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  38. Is Mobil1 5W30 approved for use in 2011 and up General Motors vehicles that call for dexos?

    As of this writing Mobil1 is licensed under the dexos specification and can be used in 2011 and up GM vehicles.

    For more information, please read General Motors dexos oil in our Detailed Topics Section.


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  39. Is the oil filter sold by the maker of my vehicle the best one to use?

    The word “BEST” could depend on a great number of factors. For instance there are filters which can remove smaller particles [micron rating] than the original equipment manufacturer (OEM) part. This might be considered best under some circumstances. The problem is, such a filter may restrict oil flow or clog prematurely.

    There are many factors to consider in oil filter performance. The OEM does a good over-all job in this category, and I feel they are the best choice for most people.

    A more detail article, on oil filters, is in our Detailed Auto Topics section under All About Oil Filters.

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  40. Is there a way to look at a fuel filter and tell if it needs to be replaced?

    I am not aware of any way to look at a fuel filter and judge its condition. The flow rate could be tested, but since the filter would have to be removed, it would not be cost effective. Since most fuel filters are inexpensive and relatively easy to replace, they are normally replaced based on mileage and performance.

    I have found, when a fuel filter appears to be old, asking the client when it was last replaced works pretty well.

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  41. It is time to pack the wheel bearings on my truck. Is there any problem changing to synthetic grease when packing bearings?

    Synthetic grease will give great service with your wheel bearings. Thoroughly clean all the old grease with a clean solvent. Allow the bearings to dry and then pack them with the synthetic product. As always, replace any wheel seals and lubricate the seal surface with a light coating of grease as well.

    Please see our Detailed Topic article Adjusting Wheel Bearings for far more details.

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  42. My car calls for 5W30 oil and this seems very thin for the hot climate I live in. Would 10W30 be a better choice?

    Both 5W30 and 10W30 have a hot viscosity of 30 weight. The 5W30 adds the advantage of being able to respond like a 5 weight oil at cooler temperature. It can also improve fuel economy and lower emissions. I do not recommend substituting a non-approved oil in any vehicle.

    If temperature extremes and operating conditions are a concern I would recommend switching to a synthetic product of the same viscosity. Also more frequent change intervals will help a great deal with viscosity concerns. Please, look in the Oil, Lubricants and Gasoline section under Should I switch to synthetic oil, for more details.

    A more detailed article on oil viscosity is in our Detailed Auto Topics section under Oil Viscosity.

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  43. My car has started to use oil, should I switch to a heavier viscosity?

    I feel the same viscosity, recommended by the manufacturer for new vehicles, is good for the life of the engine. Thicker oil will not help oil consumption. It may make it worse. Thicker oil stays on the cylinder walls longer and may result in additional consumption. Add to this the problem of raised oil volatility damaging the catalytic converter. Best is to stay with the recommended oil and simply change it a bit more often.

    A more detailed article on oil viscosity is in our Detailed Auto Topics section under Oil Viscosity.

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  44. My car manual recommends I use 5W30 oil, would you still use the recommended type even when the car has high kilometers and is over ten years old?

    Yes, the same viscosity will work well for the life of the engine. I feel it is a misconception about thicker oil and older engines. Thicker oil tends to boost oil pressure, which is not needed or desirable. At the same time it puts more oil on the cylinder walls which can increase oil consumption. Another problem is, oil drain-back. Thicker oil cannot drain to the pan as fast. On older engines with oil passages possibly restricted this may be an issue.
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  45. My Chevrolet calls for dexos1 oil, is this the same as viscosity?

    The dexos specification refers to a license, purchased by oil producers, and not actual viscosity of the product. At this time all General Motors gasoline powered vehicles, using dexos1 have an equivalent SAE viscosity of 5W30.

    For more information, please read General Motors dexos oil in our Detailed Topics Section.


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  46. My owners manual says I should change my oil every 5 month or 5,000 miles. I drive about 2,000 miles every five months. I do not understand why I should change the oil with only 2,000 miles of usage. Does oil go bad in five months time?

    Two-thousand miles in five months, means short trips or lack of use. Short trips are severe service for an engine and greatly increases sludge and acid buildup. Under these conditions moisture tends to build up in oil. This forms the acids and sludge, which pass through the oil filter. Under these conditions, I suggest even more frequent changes, without regard to mileage.

    Best would be to drive the vehicle more, particularly on longer trips. This allows the heat of the engine to boil off much of the moisture.

    A more detail article on change interval is in our Detailed Auto Topics section under The Sad Truth.

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  47. My power steering fluid was low and the pump was making noise. I added fluid and the noise went away, but after I turned off the engine, the fluid came pouring out the reservoir opening.

    The fluid level getting low indicates a leak in the system. Low fluid, allows air to enter the system and produce noise. When fluid is added, the air is pushed into the system and compressed by the fluid pressure. When the pump quits turning the pressure drops and the compressed air expands. When the air expands the fluid is pushed out. First locate and repair the leak. Once the leak is repaired, filling and bleeding the system of air, should cure the problem.
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  48. My truck is equipped to run on flex-fuel. If I switch to E-85 will my fuel mileage go up, down or stay the same?

    Ethanol produces about 33% less energy per gallon than gasoline. Switching to 85% ethanol will result in a 28% drop in fuel mileage. For more information, please see our Detailed Topic, Ethanol Fuel, Good or Bad?
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  49. My vehicle calls for 0W20 motor oil which seems awful thin. An internet forum makes a compelling argument that 5W30 would provide much better lubrication.

    Engine oil today does far more than lubricate the engine. It must also operate variable cam timing, hydraulic tensioners on timing chains, resist high temperature viscosity shear and not damage the ultra-expensive catalytic converters. All these things and more must also be optimized over a wide range of temperatures. Deciding on the proper viscosity for engine oil is a very delicate balancing act. OEM engineers design and test the engine under an immense number of conditions. Their recommendation takes far more factors into account than even petroleum experts have access to. To avoid unforeseen problems, the manufacturer’s recommendation should always be followed.

    A more detailed article on oil viscosity is in our Detailed Auto Topics section under Oil Viscosity.

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  50. My vehicle calls for premium 93 octane fuel. Can I substitute regular fuel?

    Engines that specify premium fuel use higher compression than other vehicles. Compression is roughly the amount the fuel/air mixture is “squeezed” before being ignited in the engine. The more the mixture is compressed [high compression] the more power is produced when it is ignited. This makes high compression engines more powerful than lower compression models and also makes the use of high octane premium fuel necessary.

    Octane slows the burning process and prevents engine damage. With high compression engines and low octane fuel, the fuel/air mixture may explode before the ignition fires. When this occurs, the piston is being forced to travel upward by the crankshaft, while the combustion process is driving it down the cylinder. This phenomenon is also know as detonation, pining, valve rattle or valve clatter. Severe engine damage may quickly occur. Only high octane fuel should be used in engines that specify its use.

    For more information on valve clatter see our article Valve Clatter, Spark Knock, Pinging and Pre-ignition.

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  51. My vehicle has 160,000 miles and the U-joints have started to squeak. There are no grease fittings in the present joints. Should I replace the joint with the type that has a grease fitting?

    To allow a U-joint to be greased, there must be leakage at the seals. This leakage allows the old grease to escape, when new grease is added. This is okay, if the joints are lubricated every 5,000 miles or so. This is very inconvenient and often neglected. Without lubrication the joint will quickly fail.

    With the sealed universal joint, nothing gets in or out and they normally last 150,000 plus miles with no service. I would recommend using the exact non-lubricating type joints.

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  52. My vehicle has about 50,000 miles and I am interested in switching to synthetic oil.

    Synthetic oils are much tougher and much better at cleaning an engine than conventional petroleum products. The synthetic oil will go to work to clean any sludge buildup that was present in the engine. Any sludge that is broken up will need to be filtered out. This may restrict an oil filter very rapidly. I recommend oil filter replacement within 1,500 miles after switching from conventional to synthetic oil. After oil filter replacement the oil should be topped off as needed.

    For optimum engine life, synthetic oil should still be replaced at 3,000 mile intervals, unless the average trip is over 20 miles. Many synthetic oil producers recommend longer change intervals and the product is capable of longer life. The problem is, synthetic oil gets just as contaminated as regular oil, perhaps more so. Changing the oil is the only way to insure removal of a lot of these contaminates.

    A more detailed article on synthetic oil is in our Detailed Auto Topics section under Should I Use Regular Or Synthetic Oil.

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  53. My vehicle has been stored for about a year and I am concerned about the gasoline in it. Should I add fuel stabilizer before I try to start it?

    Fuel stabilizer works when added to fresh fuel, before it is stored. It will NOT rejuvenate old fuel, and no additive will help. Best would be to drain the tank, dispose of the old fuel and fill with fresh, before starting. If not, you might try to dilute with fresh fuel, drive until half empty, refill and repeat several times in rapid succession.
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  54. My vehicle has never used oil until I recently had an oil change. I have had to add oil twice (1000 miles) since the change. What could have happened with just an oil change?

    You did not mention any leakage. A loose oil filter or drain plug can cause quite a bit of oil to be lost. Assuming no leak, changing from the brand of oil that has always been used sometimes causes oil consumption. The additives in different oils are sometimes incompatible. This can result in oil usage. Best is to return to the original brand of oil and see if the problem starts to subside.

    Another possibility would be an internal engine problem. Though this is not likely, some type of failure could have coincidentally occurred around the same time. If the oil was drained and the engine inadvertently started, without adding oil, it may not be coincidental.

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  55. My vehicle is not driven every day and I only put about 6,000 mile a year on it, mostly very short trips. Can I change my oil once a year?

    Not being drove is very hard on an engine and so are short trips. This type of use is normally considered extreme service and the change recommendation for extreme service would apply.

    When an engine is started, the temperature begins to rise. Within minutes it will rise to 180 degrees Fahrenheit, or more. When turned off and allowed to sit, the engine cools. Heating and cooling may cause moisture to condense in the crankcase.

    Moisture attacks internal engine components and may turn to sludge. Moisture also passes through the oil filter. Moisture is removed when the oil reaches and exceeds 212 degrees Fahrenheit. At this point it turns to steam and is drawn out of the engine by the crankcase ventilation system. Unfortunately, with short trips this does not occur.

    I suggest changing to synthetic oil under these driving conditions. I would also recommend going no more than six months between oil changes, even with synthetic oil.

    A more detailed article on synthetic oil is in our Detailed Auto Topics section under Should I Use Regular Or Synthetic Oil.

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  56. My vehicle list a specific automatic transmission fluid, is this just marketing or should I use only the recommended fluid?

    Many vehicles have a specific fluid recommendation. Among these are Honda, with their own fluid, Ford with several versions of Mercon, and Chrysler products. Often fluids are formulated with specific additives to address concerns in the design of the unit. AGCO does not substitute from the recommended fluid.

    For more information, see our Detailed Topics article, Properly checking transmission fluid.

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  57. My vehicle manufacturer says that the automatic transmission fluid does not need replacement, unless I tow a lot. I do not tow, it has 155K miles and has never been changed. Change or leave it alone?

    Manufacturer's realize the odds of problems from improper service, are greater than the odds of problems from no service at all. The wrong fluid, not enough fluid, the wrong filter or a filter not properly installed will ruin a transmission. Their recommendations are based on this and a supposed service life of 100,000 miles.

    With proper service, a transmission will last longer. Lack of service may cause failure from a plugged filter, debris and depleted fluid. For a transmission with no service for 155,000 miles, any damage that will be done has likely already begun. While it cannot hurt, I see little advantage to servicing the transmission at this point.

    For much more on proper transmission service, please see our article Transmissions and proper service.


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  58. My vehicle says synthetic oil should be used. Is this the same as 5W30?

    No, synthetic refers to certain standards that the oil must meet regarding load capacity and many other factors. It does NOT mean what the oil is made of and is not the same as viscosity, which is resistance to flow. The expression 5W30 is a viscosity rating from the Society of Automotive Engineers or SAE. The five is the low-temperature viscosity, W means winter use is acceptable and 30 is the high-temperature viscosity. Only oil listed as synthetic should be used in vehicles that specify synthetic and the proper viscosity should also be used.

    A more detailed article on oil viscosity is in our Detailed Auto Topics section under Oil Viscosity.


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  59. Recently an oil change shop told me my engine was full of sludge and should be flushed. I have no symptoms, should I be concerned?

    Engine flushes are one of the more popular wallet flushes sold. Chemically flushing engines is not recommended and can cause harm in many instances. A far better procedure is to use the natural detergent in oil to clean the engine, changing the oil and filter at short intervals and several times. For instance changing the engine oil and filter at 1,500 mile intervals, three times, will help remove buildup and will never harm the engine.

    Please see our Detailed Topic Fuel Injection and Wallet Flushing for more information.


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  60. Should I have the fuel injectors on my car cleaned to improve my gasoline mileage?

    Routine cleaning of fuel injectors are unnecessary and will not improve fuel mileage. Any quality brand of fuel contains detergents and injectors are designed to self clean. We see few cases of injectors that need cleaning. Even with dirty injectors we find, the symptom is normally rough idle and not poor mileage.

    A failed injector, stuck open or closed could reduce mileage, but would likely not be helped by cleaning. Buying quality fuel is a better investment. If mileage is below normal for the vehicle, having the fuel management system checked would be a better idea.

    Please see our Detailed Topic Fuel Injection and Wallet Flushing for more information.

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  61. Should I switch to synthetic Oil?


    Synthetic oil is much tougher and much better at cleaning an engine than conventional petroleum products. If the engine has any sludge buildup, the synthetic oil will go to work to clean it. Any sludge that is broken up will need to be filtered out and this may restrict an oil filter. I recommend the oil filter be replaced within 1,500 miles of switch from conventional oil to synthetic.

    For optimum engine life synthetic oil should still be replaced at 3,000 mile intervals, unless the average trip drove is 20 miles or more. Many synthetics oil makers state longer change intervals and the product is capable of longer life. The problem is synthetic oil gets just as contaminated as regular oil, perhaps more so. Acids and other liquid contaminants can build up in oil and changing the oil is the only way to insure removal of a lot of these contaminates.

    An additional issue is, if there are any leaks that were being masked by the sludge, they may be revealed by the cleaning.

    A more detailed article on synthetic oil is in our Detailed Auto Topics section under Should I Use Regular Or Synthetic Oil.

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  62. Should I try to find fuel without ethanol for my vehicle?

    Ethanol is not without drawbacks, but modern vehicles have very few problems using E-10 or 10%. If the vehicle is designed to run higher percentages, as with flex-fuel, the biggest drawback is a loss of fuel mileage. Even antique vehicles can run on E-10, with proper retrofitting. Many fuel stations that advertise 100% gasoline, are unbranded. I prefer E-10, from a high-volume, name brand station, to a private label 100% gasoline. For more information, please see our Detailed Topic, Ethanol Fuel, Good or Bad?
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  63. Should I use high-mileage formula oil in my older vehicles?

    The oil originally specified, by the vehicle manufacturer, is the best oil for the life of the vehicle. I feel high mileage oils come more from the marketing department than engineering. With oil, as with anything on the vehicle, lowest cost is obtained by preventing rather than trying to repair problems. Using the oil specified by the manufacturer, the OEM oil filter and replacing it on a regular basis will prevent problems. There is nothing in high mileage oil that will undo damage from previous neglect.

    For more information on oil change intervals read our article The Sad Truth and for more on oil filters read All about oil filters.

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  64. Should power steering fluid ever be replaced?

    Power steering fluid acts as a hydraulic fluid, seal conditioner, coolant, cleanser and lubricant to the system. As such, it is subjected to quite a bit of deterioration and the additives are depleted over time. There is also the high cost of replacing steering gears and pumps to consider. I recommend replacement between 50,000 and 100,000 miles.

    Many manufacturers do not add power steering fluid replacement to their maintenance schedules. I believe this is due to a short-sighted attempt to make maintenance costs appear lower. To the vehicle owner I think overall lowest cost is far more important.

    Power steering fluid is easily replaced by simply drawing the old fluid from the power steering reservoir and adding replacement fluid. It is not necessary to remove all the old fluid as dilution and repeating the process a few times is very adequate. Also be aware that different vehicles have different type power steering fluid recommendations.

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  65. Should the lubricant in the rear differential be replaced?

    All lubricants benefit from periodic replacement. Additives become depleted over time and debris suspended by the lubricant becomes a problem. This is a particular problem where there is no filter, such as the rear differential.

    Under normal driving, I recommend the differential oil be replace between 50,000 and 100,000 miles, with the recommended lubricant. When towing it should be replaced more often. It might also be a wise investment to convert to synthetic oil, if your vehicle does not already use it. Also be aware that many limited slip differentials require additives or special oils.

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  66. Since new, I have used synthetic oil in my vehicle. On the last oil change the dealership accidentally put regular oil in it. I have heard this will damage my engine.

    It is best not to change the brand of oil, conventional or synthetic, as additive packages vary. Some are not fully compatible with others. For instance changing from Exxon to Castrol or vice versa. Changing from synthetic to conventional oil is the same. As long as the additives in each are compatible, there will be no damage. Even if not, slight oil consumption for a period of time is normally the worse symptom.
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  67. The fuel mileage on my Toyota has really dropped lately. I’m down about eight miles per gallon from the mileage I was previously getting. The check engine light is not on and I see no apparent reasons for the decrease.

    Eight miles to the gallon is a substantial drop. Many things can contribute. Since the check engine light is not on I would check to see if the engine is getting to full temperature. An engine with a stuck thermostat may run far below normal temperature and this will drastically affect fuel mileage.

    Also the sensor that reads engine coolant temperature (ETC) should be checked. Failure of this sensor to read correctly will disturb the output of the engine computer. The computer will mix more fuel per air volume for an engine it thinks is below normal temperature. It may also not allow the transmission to shift to overdrive, also decreasing mileage.

    For more information, please see our Detailed Topic, Engine Thermostats, Fuel Mileage and Over Heating.


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  68. The fuel mileage on my vehicle is lower when my wife drives it than when I drive it. How can this be?

    Driving style is one of the largest factors in the fuel mileage received. Different driving habits can increase fuel mileage up to five miles per gallon, on certain vehicles.

    For more information, please see our Detailed Topic, Driving Tips for Better Fuel Mileage.


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  69. The owner's manual of my 2011 General Motors car says use only dexos1 oil. Is this a new type of oil?

    Dexos is not a product at all, rather a license that oil producers must buy from GM in order to be approved. The dexos license requires oil to pass specific test. GM claims specific properties tested for are necessary in their automobiles.

    For more information, please read General Motors dexos oil in our Detailed Topics Section.


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  70. What do the numbers and letter like 10W30 mean with regards to oil?

    The W stands for Winter which means the oil is acceptable for all seasons. The ten reflects the cold properties of the oil and 30 the hot properties. For example 10W30 oil can flow like a ten weight oil when cold (0 degrees Celsius) but still offer 30 weight protection when hot (100 degrees Celsius.)

    A more detailed article on oil viscosity is in our Detailed Auto Topics section under Oil Viscosity.

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  71. What does the word weight mean in relation to engine oil, like five weight oil?

    Weight is a scale used by the Society of Automotive Engineers or SAE to classify viscosity characteristics of lubricants. Viscosity is resistance to flow at a given temperature. A low weight, such as five, will flow much faster at a given temperature than a higher weight, such as seventy-five. Temperature must be considered as oil tends to flow more slowly when cold than when hot.

    Viscosity is often measured in centistokes (cSt) which is roughly, the time it takes a fluid to flow through a given sized orifice at a given temperature, often 40 degrees Celsius. SAE five weight oil is roughly equivalent to two centistokes.

    A more detailed article on oil viscosity is in our Detailed Auto Topics section under Oil Viscosity.

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  72. What happens if I over fill my engine oil?

    Over filling oil is a matter of degree. With one quart or less it is unlikely to cause a noticeable problem. If more oil is added the level rises, the crankshaft will begin to pull oil up and whip it into a vapor. This will be drawn into the PCV system and can cause damage to the catalytic converter(s) and increase oil consumption.
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  73. What is the best engine oil?

    There is no best engine oil, instead there are many specifications various oils meet that make them proper for a given engine. The Society of Automotive Engineers or SAE, the American Petroleum Institute or API and others insure oil meets the proper specifications. What is best for one vehicle may not work in another. The best oil is the oil that meets or exceeds the specifications of the manufacturer of the vehicle. Brand is less important than selecting the proper product. Most major oil producers sell products that meet manufacturer’s specifications as long as the proper product is selected.
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  74. What is the difference in 5W30 and synthetic oil?

    These are two different matters entirely. The 5W30 is a Society of Automotive Engineers or SAE viscosity rating. Viscosity is basically a resistance to flow or similar to how thick the oil is at a given temperature. Synthetic concerns certain quality characteristics of the oil. For example, a product can be 5W30 and synthetic, synthetic blend or conventional oil.

    A more detailed article on oil viscosity is in our Detailed Auto Topics section under Oil Viscosity.

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  75. What will happen if you put E-85 fuel into a standard gas motor?

    If the vehicle is not designed to run on E85, the check engine light normally comes on, due to excessive lean condition and the vehicle will lose power. Some vehicles may quit running, others may run very poorly. In one case we saw a fuel pump ruined, possibly the same affect as running out of gas? Continuing to run the wrong fuel can cause permanent damage, much like running the engine too lean.

    For more information on fuel pumps and why they fail, please see our Detailed Topic, What Causes Fuel Pumps to Fail.


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  76. Where can I dispose of engine oil?

    Best is to locate a recycle center in your area. Virtually all used motor oil is recycled, most to make heating oil. Many oil change shops and some parts stores will take used oil for recycling. Some municipalities also have centers set up for the purpose. A call to the local Department of Environmental Quality should provide a list of local recycle facilities. Never mix anything with used motor oil as this can make it hazardous and not acceptable for recycling.
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  77. Where does the engine oil go when the dipstick is low?

    Engines generally lose oil in two ways. Oil may leak pass the piston rings or valve guides and be burned in the engine. If excessive, this requires engine repair to correct. Oil may also leak externally, due to bad gaskets and seals. There will normally be evidence of such leakage, such as oil under the vehicle or a burning smell.

    Losing a small amount of engine oil is considered normal by many manufacturers of vehicles. They contend that proper lubrication requires a small amount of oil leaking passed the piston rings. This will normally account for one quart of oil or less in about 2,000 miles of driving. Losing more oil may be considered a problem and should be investigated.


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  78. Which engine oil should I use?

    Selecting the proper engine oil can be complex. Fortunately, all vehicle manufacturers have done the hard work and recommend specific oils for their vehicles. The owner’s manual will list the proper oil for the application. If the owner’s manual is not available, a specification guide for the vehicle can often be used. Be cautious of any recommendation by a dealership, oil change or repair shop that is not the same as the manufacturer recommends.

    A more detailed article on oil viscosity is in our Detailed Auto Topics section under Oil Viscosity.


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  79. Why did Ford revise the specification on the engine oil in many of their V-8 engines from 5W30 to 5W20?

    The lower viscosity oil provides better fuel economy and may be easier on the catalytic converters. Ford also felt 5W20 provides more than adequate lubrication for the engines specified.
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  80. Why do mechanics wipe off the oil dipstick and then put it back in before taking an oil level reading?

    When the engine is running, oil is slung around inside the crankcase and onto the dipstick. This could result in an incorrect reading. By wiping the dipstick clean and reinserting it, a more accurate level of oil is displayed. The engine should also be allowed to sit without running for two minutes before taking a reading. This allows more of the oil circulating in the engine to return to the oil pan and gives a more accurate reading.
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  81. Why does driving faster burn more gas?

    Gasoline is energy and energy is required to overcome inertia and friction. The faster a vehicle is driven the more energy, in the form of gasoline, is required. Modern vehicles also learn the way they are driven. More aggressive driving will change shift points and engine tune and will consume more fuel to increase power output.

    For more information, please see our Detailed Topic, Driving Tips for Better Fuel Mileage.


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  82. Why is synthetic oil not recommended for older engines?

    There is no reason synthetic oil cannot be used in an engine, regardless of mileage. Different brand oils use different additive packages and switching brands of oil, whether synthetic or conventional can lead to oil consumption. That aside, with well maintained older engines there should be no problem whatever. With engines that have not been well maintained, the detergents in synthetic oil can remove crud that is temporarily concealing oil leaks, and reveal leakage.

    When changing to synthetic oil I have also found it is wise to replace the oil filter, about halfway through the change cycle. This may help prevent any sludge that is being removed by the synthetic oil, from plugging the oil filter. For instance, replace the oil with synthetic, drive 1,500 miles and replace the oil filter. Top off the oil and then replace oil and filter at the normal change interval.

    A more detailed article on synthetic oil is in our Detailed Auto Topics section under Should I Use Regular Or Synthetic Oil.


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  83. Why would engine oil turn milky brown in color?

    The most common cause of milky-brown engine oil is coolant contamination. This can result from leaking intake gaskets, blown or leaking cylinder head gaskets, a cracked cylinder head or even a bad radiator or engine oil cooler. The situation is very serious as even a very small amount of coolant destroys the ability of engine oil to protect the engine. Very quick diagnosis and repair are mandatory to prevent engine damage.
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  84. Will it hurt my engine to temporarily mix petroleum with synthetic oil?

    Surprisingly, petroleum can and often is labeled as synthetic in the United States. The word synthetic has been found to be a marketing term, relating to certain characteristics, and not what the oil is made of. While I don’t advocate mixing different brands of oil, because of additive differences, what is labeled synthetic and conventional oils are compatible. Other than additive differences they can be mixed without damage to the engine.

    A more detailed article on synthetic oil is in our Detailed Auto Topics section under Should I Use Regular Or Synthetic Oil.

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