I think the ethanol and octane questions are separate things. You can always go with a higher octane. It will only hurt your wallet. The problem comes with lower octane. Personally, I have had problems with ethanol in small engines like chain saws and mowers. I also had a problem when I was a kid with a car made in '74. Some of the rubber in the fuel system just dissolved over time. For quite awhile I would only use (what at the time was called) gasohol if I planned to burn the whole tank. For the last 10 or 15 years I have been using 10% alcohol in everything bigger than my lawnmower all the time and have had no problem.