Thanks B.C. My half-brother is a retired GM executive and he was the first one to tell me about the "1 or 2 mpg EPA" thing. He didn't get into all the rest of the technical stuff YOU did, and he probably doesn't even know all of that.

But, overall, yours was the answer I was looking for. I made my post so long, so as to get SOMEONE who REALLY KNEW to answer. Not sure how you would have answered had I just asked: "Why zero weight oil?", but I AM happy with your answer. Thanks again.

I"m going to print and save it, if you don't mind.

But before I go, one thing: Could you have included 0W40 in your chart?