crankcase oil

the crankcase oil for a 2stroke is the pre-mix. It drops out into the crank case.

If you mean tranny oil, I would use specific 2 stroke tranny oil made for dirt bikes and quads. It's a little different than just regular motor oil.
 
i use pensoil 10w40 in all my bikes/quads the royal purple will work fine. I also change mine after every ride also. cheap maintance/protection
 
I use Mobil One Synthetic Racing 4T it can usually be found at walmart it's basically streetbike oil. Shifts like butter!
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Ive been running Amsoil 10w40 full synthetic motorcycle oil for 2 years putting
2600 miles on my 2 stroke atv and motorcycle. Not one clutch failure! Just make sure the oil has no friction modifiers. Friction modifiers will lead to clutch slip ending up in failure. Rotella t dose ok but in my 4 stroke after a summer of using it the clutch started slipping. So I would not use rotella