http://forums.pelicanparts.com/showthread.php?t=367300
http://ultimategto.blogspot.com/2007...yler-jark.html
Apparently some of the newer oil being sold in the last couple years has drastically reduced the amounts of certain additives due to stricter EPA requirements (Zinc, Sulfur, Phosphorus). Sounds like these additives alone are actually quite valuable, especially when it comes to people pushing their motors. Also I read the lack of these additives could be a partial cause of why we see so many turbo center section's needing rebuilds now a days while in the older days, vehicles that didn't even use BOV's had their turbos last quite a bit longer.
Anyhow just thought I'd share this so others can form their own opinions from it. I'm going to change my oil tomorrow before I hit the track Sunday, and may go check out all the oils they have at Napa and see if I can find some pre-SM rating stuff.