Any quality brand name oil compatable with wet clutches is fine. I highly recomend full synthetic due to the high rpm these engines run. For dino oil you need to match the oil weight to mfg recomendations, however a full syn oil doesnt make much difference due to its superior lubrication. I use Rotella T-6 full syn 5w-40 oil that is compatible with wet clutches
It doesn't have to be wet clutch compatible oil since scooters don't have a wet clutch.
I use the same oil as in my motorcycle just because it's easier.
10w40 semi synthetic, no problems the last 9 years.
Edit:
Sorry, just realised this thread is not about scooters. My bad.
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