There's all kinds of talk about how E85 (85 percent ethanol, 15 percent gasoline) isn't very energy efficient, delivering roughly 75 percent of the Btu heat energy of gasoline, which is true. It's also true that E85 delivers an octane rating of somewhere around 105, which beats the hell out of 91 octane here in California. So let's take advantage of the additional octane. For the last 100 years, engines have been designed around pump gasoline's low octane rating. So if mileage is a consideration, then build a small-displacement V-8 like a 302 Ford with 12.5:1 to perhaps as much as a 14:1 static compression ratio and match it with a short-duration roller camshaft and match it with some good aluminum heads. Now we use that high cylinder pressure to get more bang out of that 105-octane fuel. It's entirely possible that this higher compression will make up that 25 percent loss in mileage and perhaps more with E85 and you end up with a very fuel efficient, performance engine that still makes good power. This would work.