Originally Posted by Jordo!

I think the key value here is latent heat of vaporization vs. amount of fuel needed to achieve peak torque, which is a factor related to stoichiometry -- check out p. 117 on down at this link.

http://martysgarage.info/manuals/bell2ttuning.pdf

It's from A.G. Bell's book on fueling 2-stroke engines, but he has the exact same formulas/rationale in his 4-stroke supercharged tuning book.

Anyway, in theory, less efficient, but more energy ultimately produced as a consequence.

Now, if E85 ends up breaking about even, then it's just less efficient, but has a higher auto ignition threshold and higher octane, in which case never mind my other point