This was the very reason I tried e85. I heard a car needs more fuel as e85 contains less energy so you burn more. Others say e85 makes more oxygen in the exhaust stream so your car leans out the afr and performance suffers. Others say e85 has the octane of 110 so for a high compression engine it will rock. How can it rock if its going to run lean?
Anyhoo I got an instant 9mpg, the engine seems to be quieter and the ima system acted as one would think. I refueled at half a tank and confirm the mpg increase during a brief spell of room temperature weather.
When the weather was a high of 32 and 70 miles I managed a dtc for lean condition.