How can I tell if an oil is right for my engine?
With so many people trying to sell specialty oils and additives most advice on oil is not very useful. When buying oil your main concern should certifications used by both petroleum and engine manufacturers.
If you have a gasoline engine, the easiest way is to match up the weight of the oil you need and check the back for the American Petroleum Institute’s “starburst” mark. This is a circle that says “FOR GASOLINE ENGINES” on the inside with “American Petroleum Institute Certified” around the edge. Oils that carry this meet the latest standards for wear and fuel economy. These should be safe to use in any gas engine except for one notable exception: see below.
If you have a diesel engine or you need to know more about the oil, look on the back of the bottle and you’ll see the API “donut.” This means the American Petroleum Institute has tested the oil and it meets specifications created in cooperation with most major automakers.
Top half: This is the oil’s performance level. Oil for gas engines will be labeled “S” followed by a letter while diesel oil will be labeled with a “C” followed by a code. New oil performance classes are compatible with previous ones so you can use an oil with the same or newer grade in your engine. For example, if your engine needs SJ-certified you can use the newer SM oil.
Center: This is the oil’s viscosity. Modern oils are thin when cold and thicken as they are heated allowing both easy starting and proper surface coverage. 0w oil has the same viscosity as water while 30w has the same viscosity as maple syrup.
Bottom half: Low friction oils increase efficiency and therefore fuel economy. Gasoline engine oils that meet the API’s requirements have the phrase “Energy Conserving” on this section, while diesel engine oils will say “CI-4 Plus.”
More information on API’s certification can be found here: API: API Quality Marks
Will modern oil destroy flat tappet cams?
The amount of zinc dithiophosphate (ZDDP) in oil has been reduced in modern oils because they can cause problems with catalytic converters. However, this anti-wear compound is critical on flat tappet cams especially when they are breaking in. Zinc additives are on the market which can be mixed with modern oil while some non-API certified racing oils have the high levels of zinc needed to prevent cam failure.
Flat tappet cams are found on most vintage British cars, old motorcycles, a few high performance America engines, and some race engines.
Can I use car motor oil in my motorcycle?
There has been a lot of confusion on this point over the years, especially as motorcycle and car engines have become more and more alike. The Japan Lubricating Oil Society and Japanese Automotive Standards Organization have created a motorcycle-centered certification, MA, which can safely be used in most motorcycles. Oils tested by them will have a rectangle that says “JASO MA.” Many oils meet the standard but have not been certified. These will have some text showing that the oil meets the JASO MA standard. Most diesel engine oils meet this standard.
Synthetic motor oil should not be used in motorcycles with wet clutches. A wet clutch sits in the crankcase and is covered in oil. If a synthetic oil is used, friction may be reduced to a point that the clutch cannot properly engage.
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- What is the Best Synthetic Motor Oil?
