I have run alky powered drag cars, and the general rule of thumb was that you need to supply almost twice as much alky as gas to a motor. That said, it would also make about a 1/4 more power. Yeah, you can build a e-85 only motor to get good milage out of it, but with a flex fuel motor, e-85 will always get worse. Making the alky burn most efeciently negates the ability to run gas.