10w30 oil they r lite an rev fast u don,t want a heavy oil oil like 20w-50 unless itr,s a bit flogged out!! then go the the thicker oil. I find the lighter oil oil fine an it helps MPG!! Read cheaper 2 run!! but everybody has there fave!! In my 350 HQ I ran pennzoil streetmachine oil @ 20-50 it loved it, big heavy always overreved no stress showed on the bearings ever!! so try a few an make yr own choice!! enjoy!!