The EPA lists the GM at only 16 MPG highway with E85. That is 30% less than the 23 MPG a GM gets with gas. If you are paying $2.90 for gas in your area, a $.70 per gallon lower cost for E85 is only a savings of 24%. So actually you would be losing!
It's true that EPA mileage figures are suspect and you might do better but even with a bit more favorable figures, you wouldn't be gaining much...if any. And you would have to stop and fill your tank 30% more often.
"There is no free lunch"...