I used a fancy car oil that was on offer in the old 1100 Virago. When it was cold the clutch would slip. As it warmed up the clutch stopped slipping. It's a v twin with good torque and not much power so maybe this highlighted the fault. Maybe it wouldn't affect a smaller bike but I won't be doing it again. I'm running on morrisons own at present. The older , higher mileage the engine is , the less critcal the oil is. However with a high reving, high performance track day bike, with a blueprinted engine running fine tolerances, the oil can make the difference of a few tenths of a second per lap. The most important thing is that you have some in and it's not too dirty, the rest is semantics and opinion