I'll preface this by saying that I know very little about E85 and such, and I'm asking these questions to learn, not to be a jerk or anything. I guess I'll ask the same question again. The difference in those things you mentioned, is it significant? Going from E-0 to E-10 doesn't seem to negatively hurt every car on the road (including 'performance' cars) except in maybe fuel mileage. I suppose going from E-85 to E-75 may not be comparable to going from E-10 to E-0, but I don't know that for sure. As for the octane rating that you mentioned in post #16 above, the reading I've done suggests that the difference in actual octane (which is small anyways) doesn't make much significant difference in the knock protection; it's the cooling effects of the ethanol that do that, and E70 is every bit as good at that as E85. The difference in effective octane is, at most, a degree or so of max timing on a high horsepower setup. Correct me if I'm wrong.