Any oil that has the JASO rating is OK for wet clutches. Best to use one that has the JASO Ma2. Any 10w40 in either conventional or synthetic is always fine. In fact any 0-15w40 is fine. No w50s. Many people use the Rotella T5&6. Personally I don't use diesel engine oils in gas engines...and would rather use high RPM, high heat racing synthetic motorcycle oil made for shared-sump systems in my four-stroke powersport engines so I pay the extra.. and use Castrol Power 1 or Power RS. I haven't changed my oil in over two years and it's just now getting enough color that I can see it on the stick without looking for the shiny line. Think I will change it this winter. Relax people..it only has about 500 miles on it..lol