got a circle track friend that runs a 500 holley 2bbl and mixes it 60 % e85 and says it run better and cooler. when it's 100 out side and you're running around in circles for 20 laps he says no heating problems even when you are under yellow. he only had to go up 1 size to get the plugs to color right. he tried 2 and was a little too rich.