You might want to go to the Castrol web page, or call their 1800 number and find out about their zinc, level. I think it was at .083%. And find out what Zinc is for. Start up is the damage. No oil preasure. Zinc helps fight that.Thanx 4 the info guys.I have a little time yet to think about wat to use, maybe i should stick with Castrol 5w30 conventional oil,i used it in my 96 silverado for years.plus i change my oil way earlier than the specs say to.