The Ethonal burns cooler than gas , that is why you need more compression to make it fire off and make as much power as regular fuel .. The nature of Alcohol has that cooling affect on the engine , it cools the air charge a lot better than gas would . The carb , intake all the way to the intake runner will be cool, and sweat , and that some time give you that moisture in your valve covers that we all hate .
Any fuel leaned down enough will burn a piston , no matter what your burning ..You have to jet way up to burn Ethonal or E-85..