Originally Posted by Tim

Jim,

From what I understand, the motor builders aren't using oil with an increased zinc-phosphate additive - they're using oil with the additive amount that was in there a few years ago. You are right that the zinc-phosphate causes some environmental concerns, so the oil manufacturers were required to lower those levels. The oil you buy at Wal-Mart, etc. for passenger car use does not have the same additive levels from previous years, so you're losing the wear protection it provides.

That being said, I've switched from the Castrol 20-50 that I used to buy at Wal-Mart (and which I had no problem with) to the Valvoline VR-1 20-50 that I buy at AutoZone. I did this primarily to get the additive content back to the previous levels to give me a little cushion.

Tim Simmons