I put a lift and a set of 295/60/20s on my 2010. I have 3.55 gears and the larger tires impacted performance. To experiment, I put in a high octane tune. There was a noticeable difference in performance and E85 works pretty good on a high octane tune. I run E85 all the time. The mileage sux, but compared to the price of 93 octane, it comes down to a matter of preference. E85 performance is pretty good.

From a price conscience standpoint...
E85 versus 87 octane = Go with the 87.
E85 versus 93 octane = Pick em

From a "have a little fun" perspective...
Give it a try.