[richtazz]

two things. Ethanol is corrosive to fuel system parts and doesn't yield the same thermal output as gasoline. Since higher octane fuels burn slower that low octane fuels (that is how they reduce knock and thus KR) and ethanol burns much slower than gasoline, that is how Ethanol "raises" the Octane. I don't own a GTP, so I can't say for sure, but in past experience, I didn't have good luck with Ethanol fuels, especially in Hi-perf applications.