Different oils also have different additives, and some clutches need those additives to work correctly. At previous week my friend called me to look at hes bike. He told me on the phone that hes clutch is not working well. I couldn't figure out what was wrong with it, but then my friend told me that they were adding oil in it on previous day because of the low oil level.... That added oil was some other than recommend MOTOREX's(if i remember right it was VALVOLINE's), my friend had looked just for the viscosity and bought the cheapest **** he could find... Ended up burning her clutch = +100$ for the new clutch plates and springs, and about the same +100$ for the proper MOTOREX oil...