I recently bought a AC 500 ATV and I am about ready to change the oil at the 10 hr interval. The owners manual says to use 5w-30 with an API rating of SE, SF, or SG. the oil I have has an API rating of SM. Is it ok to go ahead and use the SM rating oil. If not could you explain what the SE, SF, or SG means. Also I was wondering about using synthetic oil, once I change to synthetic can I go back to regular oil or not. Thanks to anyone that can help.

 

It's important to use oil rated API SE, SF or SG as your manual says, because the newer API ratings like SJ & SM have additives to increase fuel economy in cars which may cause clutch slippage in motorcycles and ATVs. Oils rated either API-SG or JASO-MA (or both) are appropriate for use in an ATV. API-SG was the last automotive rating for motor oil considered appropriate for motorcycles. JASO is a newer oil rating system developed by motorcycle manufacturers due to the fact that API ratings after SG should not be used in motorcycle and ATVs.

There are a number of old topics on the forum where oil has been discussed extensively. You can find some of these in the archives by using the search feature, but here are a couple which include some links to web pages with more information:

Motor Oil & Motorcycle Oil Wisdom

 

Not sure exactly what the letters stand for but it has to do with duty and working with a wet clutch. You can use synthetic but it has to be able to work with a wet clutch or you won't go anyplace - clutches won't engage. Once you use synthetic, yes you can go back to dino oil. I switched back because I change oil often and the expense was a better trade off - a clean dino oil is better than a dirty synthetic. Pure economics. I can't tell you that synthetic is better because I get the same gas mileage with either, the power seems the same but I have cleaner oil all the time. Start laying out $30 bucks an oil change and that makes you want to get your moneys worth by running the oil longer. But change it for $8 to $10 bucks and you feel more comfortable about changing more often and keeping clean fresh oil in the engine.

 

SAE is Society of Automotive Engineers

API is American Petroleum Institute

ACEA is Association des Constructeurs Europeens d'Automobiles

The SA- SM are standards for bascially the year of engine.

SA was the standard for engine use in the 1950's (not really sure on the year just using it to explain)

and like was said before SM is now the standard for engines made today.

a motorcycle or atv specific oil should be used in atv's because auto oil does have additives in it.
however, where is the wet clutch on a 500 auto? or any cvt for that matter? so why would it hurt to run any recommended weight oil in a cvt machine?