I work at a small airport and have access to free 100LL AvGas (I just use the fuel sumped out of the tanks every morning). I was wondering if it would be safe to use in my stock ZX-10 and if I would have to worry about any long term effects. I know higher octane doesn't burn as well in a lower compression engine, but the only 93 octane gas I can get here has ethanol in it. The only non ethanol there is around here is 87. So which would be best for my engine, or which would be my best option: free 100LL, 87 w/o ethanol, or 93 w/ ethanol.