I don't know about all this oil stuff...my older brother only uses dino oil and not expensive dino oil either in his bikes and his '78 BMW RT has over 500K miles on it with zero engine issues, his newer RT1100 has 200K miles on it with zero engine issues...he changes the oil every 3000k miles religiously.
I've used a semi-synthetic blend in my bikes since around '99 or so, before that I used dino oil and never had any issues with clutches or engines.
I use Royal Purple synthetic in my beast and there are no issues with clutch slippage or anything.