Take the time to play with your toys and ethanol in gasoline is NOT good in any concentration, unless it is a new engine designed for it. (new cars)
Ethanol eats anything rubber, destroys seals etc. kills lawnmowers, weed-wackers, chain saws, your 67 GTO, and it CAN kill a Deuce. For a Deuce think of the five ways to make a "Rotella milkshake" of your crankcase oil, which has a lot to do with o-rings made of rubber.