and it makes a significant difference in power if you have optimized ignition timing. You just cant get away with it on pump gas. Typically you can go up as much as 5 degrees more on race fuel without any detonation, I've taken it up to as much as 8 degrees more(than a pump gas program) without detonation. Power increase is very dramatic in the butt dyno, as well as on the dynojet. I put down nearly 60HP more simply by bringing the timing map up while running race fuel.