Just pondering the mysteries of motorcycle oil again based on the other hit MCM thread "Oils ain'tiz oils" and got in touch with an oil dealer who spent half a day sending me some good info.

The attached PDF link is a 2009 oil study (White Paper) from Amsoil (through an independent research firm) that nicely describes several differences between car and motorcycle oil. As figured, the section on "wet clutch compatibility" is the most lacking in empirical data but the other tests of major oil brands is interesting to see as it's supposed to be an "unbiased" study.

One feature worth looking at is the "Rust Protection" section on page 20 of the PDF. This part may have more significant impact on C-Motos since the internal parts may or may not be made of the most rust resitant metals. It becomes double important if you have bikes that sit for extended periods of time and live in humid/salty environments.

Regarding our low performance C-moto needs, I would still bet that most any oil would suffice as long as it stays within the correct viscosity range at operating temperature - not all of them do apparently so check out the page below! High performance race bike engines, would of course see the long term benefits of better oil but our simple little low compression thumpers would probably be okay with a healthy regiment of regular oil changes.

Regardless of who's rated the "best" oil, the study does illustrate and discuss some interesting points to consider when trying to understand how oil impacts your motorcycle engine. A good read if you're really into oils!

Webpage with click-on oil viscosity results comparison after multiple cycles at 100C.

Powerpoint animated oil study walk through with voice over...

PDF Download Link: