Interesting, as 2 mpg is the difference I have seen between $3.10/gal 87 octane and $2.49/gal *E85* in both a flex-fuel Chrysler minivan and a flex-fuel Chevy Suburban on trips long enough to go through whole tanks of gas at a time.
“When I stopped using E-10 gasoline and switched to 100% Gasoline, the mileage on my pickup went from 18.5 mpg to 20.5 mpg an 11% increase in mileage.”
Mathematically, ethanol shouldn’t drop mileage that much, but that’s my experience, too. Driving the same route to/from work, I drop a couple MPG on ethanol. On gasoline, I can drive for two weeks (10 days/same trip) on a tank. On ethanol, I have to fill up on the 10th work day.