TCW is a Rating for water cooled engines, and if that's the only cert on the bottle , That means it's only been lab tested in a water cooled engine. The VERY best rating a small engine can have is JASO-FC & ISO-EGD these have been thru the most testing and can pass any test put through. IMO I would never use any oil that didnt have those ratings, but any oil that can pass all those test is pretty darn good.




"Another huge myth is you can safely use any TCW-3 certified oil in your snowmobile. WRONG! This marine rating is now very outdated as applied to snowmobiles and does not provide sufficient lubrication for many of the higher-powered snowmobile engines at sub-zero temperatures. Your higher quality oils will have a certification such as JASO-FC or ISO-EGD, so these are the standards you should be looking for."

this was taken from the AMSOIL website