Sorry, I think I was getting confused between other threads I am active in here. Then I read back some of the messages here, and I could not make any sense out of some of my own messages.
But I want to say that tranny oil is sometimes separated in motorcycles as well. At least in older motorcycles. My 1971 BMW tranny oil never sees the engine. It uses gear oil in the tranny, shaft and differential all separated from each other as well as the engine.
So I never use motorcycle oil in its motorcycle engine, I just use car engine oil. The clutch will never see any oil at all as it is a dry clutch.
I guess they don't make motorcycles like they used to. But the BMW is a rather high maintenance machine anyway and calls for the gear oil to be changed every 3K miles, unlike any cars made back then. So let's make that comparison.
-Don- Auburn, CA