Originally Posted By: Anies
Think of it this way. GM factory fills M1 in the Vette. Vette owners tend to stick with it. Both the owner and GM believe it to be good enough. Hyundai fills it with QS and it works.
I don't disagree. But I also don't believe that GM is filling Covettes (and Cadillacs too) with M1 because M1 is "better" than Pennzoil, Valvoline, Castrol, or Quaker State synthetics. Likewise, I don't believe that Hyundai is filling engines with Quaker State because Quaker State is "better" than Pennzoil, Valvoline, Castrol, or Mobile conventional. Oil companies are offering car companies incentives (in one form or another) to put their name on the oil fill caps.