I've run as high as 12.5 on E85 on the street in a heavy (3700 pounds) car with automatic and air on, still no problems with detonation. The one thing we do that we started years ago on drag cars is to install a small tank (4 gal) and just the cheapy Holley pump as an auxiliary system, with a couple gallons of race gas in it. When you're done racing for the day, turn on the valve from the gasoline tank, shut off the valve from the E-85 tank, and run the car long enough to get gas through the carb(s), then shut it off, through a shot of Sta-Bil in the E-85 tank, and put the car away for the week....

BTW, there is a fuel stabilizer on the market now made specifically for the 10% and 15% fuels, I put a 4 oz shot of it in ye 'ol shop truck (E-85) every time I fill it and don't have any problems with it either.....

Ethanol presents all the same headaches of dealing with it as methanol, just at a much lower cost....Still IMO E-85 is the best way to get away with a lot of compression in a street car!!!!!!