Originally Posted by BetaDnB
Here's what it says on page 351 RE fuel ethanol/E85
During the summer season, fuel ethanol may contain a maximum of 85%
denatured ethanol (Ed85) and 15% unleaded gasoline. The fuel ethanol
has a higher octane rating than unleaded regular or premium gasoline
and this allows the design of engines with greater efficiency and power.
This basically says higher octane = greater efficiency and power.
Actually, the above quote says that this fuel "allows the design of" engines with more power etc. It does not say if you put this fuel in your car that you will get more more or efficiency.