Quaker State 20W-50W, Valvoline 20W-50W, etc. will be fine but you MUST use the additive from now on. If you don't you will wipe out some cam lobes, guaranteed. Some have said Rotella can be used as it still contains zinc. However, I've heard that the Feds made them reduce the amount of zinc so it's not as good as it used to be.