The closest auto parts store to my house stocks most of the Amsoil line and I'm considering using their Series 2000 in my Challenger. Do you folks who run Amsoil in your race or street/strip cars use an oil analysis program to determine your change intervals? Since the stuff has a high TBN level (12), it "should" be able to last quite a while and not need to be changed as frequently as oils w/ lower TBN ratings. And, at $10 a quart, I'd hope it wouldn't need to be drained as frequently, either. Any other comments about the product are appreciated, too.