what the higher octane does, is keep the A/F mix from preigniting ( detonation ), and only ignite with the spark. ( higher heat/ compression needs it to maintain it's stabillity ).. it doesn't make it any weaker, but it also doesn't make it any stronger.. you will use more E-85 than gas because the thermal efficiency of alcohol is a little less than gas... main thing is, if your going to run E-85, you have to check the plug regularly and tune accordingly.. if you have 1 , use a pyrometer or non contact thermometer, and take EGT's, make sure they don't run too hot... E-85 could burn the engine up, if it's tuned incorrectly, but tuned correctly, just like anything, should run just fine.. I'm a hotrodder by nature, so taking the road less travled is what I do..