I picked up some 10/30 Brad Penn grade 1 cheap at a garage sale and mixed it 50/50 with some Formula Shell 10/30 that was in the stock pile , I was worried about the cat and the high zinc and thats why I went with the mix. My LS1 with 40,000 miles has NEVER has anything but dino run in it before this, and I run it hard! The motor seems to like it alot (smooth and revs up quick) and the cold start LS1 piston slap has been greatly reduced IMO. I'd like to run the BP 100% but the "catalytic converter warning on the bottle" scared me off. I know its not the best to mix oils but I have to use this stuff up somehow!, should be ok, what do ya think???