I run 100% denatured in my car because the directions in the SMC kit said that gave the best results. Alot of people say a mix of rubbing alky and water does better. When I get my car fixed, if ever, I have to go through the full tank of denatured before I can test the water/rubbing mix. I'll post my results. As of now I went from 9 psi to 18 psi with no knock on a 30 degree KB Hot Flash race chip.