What is the difference between E100 and E85 in fuel efficiency?

Question

If E100 is [near] pure ethanol, how does that affect its efficiency compared to E85 and normal unleaded? How much difference would it make under the most recent and technologically advanced engines if you used E100, E85 or unleaded petrol? And, is it true that E85 will actually give you more distance than E100 in a specially designed engine for each?

Answer 1

http://www.ilcorn.org/Ethanol/85__Ethano...

has that

E85 lowers your mileage to 2/3 of unleaded.  

By extension, E100 would be a little lower than E85.  

Answer 2

there is little difference between the two overall. the biggest difference being the fact that E85 makes it easier to start the engine when cold. fuel economy will suffer a bit more on E100, but with a little tuning you can minimize that difference.  

Answer 3

e100 would be pure ethanol, e85 is 85% ethanol, e10 is what unleaded gas is normally 10% ethanol. ethanol is worse on mileage than gasoline, e100 i would say probly is worse. who is making that, anyway. ive never seen that, do you have an old moonshine still, or thinking about tapping straight into one of thes ethanol plants they have been building around here? if its a still, just put a little aceton in it, to keep people from drinking it, it works. you can burn up to 50% e85 in your car now if its using e10. it will handle that much but dont overdo it. it might make the engine a little cold blooded so may start a little rough, but it wont hurt it.

Answer 4

Ethanol has a lower energy density than gasoline on a per mass and per volume basis.  In other words, given equal masses or volumes of E100 and E85, you get more energy out of the E85 and would therefore get more distance out of E85.