You can normally find gas stations that sell real fuel, use
http://pure-gas.org/ to find them, but they're quite expensive.
E15 is bad, i can't believe it made it through
E85 works because it's mostly ethanol, it resists detonation way more, but you use tons of it to get the power so it's not for road cars.
Also, ethanol, resists det more, contains way less power than regular gas.