This is interesting, even if it isn't really unexpected. Ethanol has less energy per gallon than gasoline, so it should take fewer gallons to go a given distance with ethanol free gas, in theory.
But the difference is fairly small, considering we are talking just 10%... worse, 10% nominally, because really 10% varies anywhere from 10% down to 0%.
Several questions:
1) how sure are you that you are really seeing a difference in the car, as opposed to driving slightly more conservatively. I know it sounds crazy or even insulting to suggest this, but studies have shown there is a high tendency to unconciously drive just a little more conservatively when testing a mod... and one of the biggest factors in mpg is in how we drive. You already admitted to having a lead foot, what if you are driving with a silver foot instead?
2) how much are you paying per gallon for the ethanol free vs the regular? In other words, are you getting more miles per gallon but paying so much more for the fuel that you end up getting fewer miles per dollar?
3) does this affect your available power? In other words, do you get a max of 138 hp with regular E10, and only a max of 130 hp with this new E0?