Ethanol reduces fuel economy, there is no mystery, it simply requires more gas to do the same work! Less energy, period.
You guys putting ethanol in and claiming better gas mileage have a bad test that you are using to calculate or your numbers are messed up, it just is NOT possible. There is no question about it!
E85 will reduce your gasemileage by 26%-34%. This range is because different manufacturer will adjust the tune for the E85, depending on how they do this depends on the results.
E10 will typically reduce the mpg by around 2%
Back on topic
This past winter in the crappy weather I was getting around 11.5mpg. Since the snow has melted and it has been a little warmer I have been seeing 13.5mpg with the winter blend fuel. This is all in town driving.
On the HWY I have got 19mpg doing 80mph with the cruise set going up and down slight hills. Again, this was winter grade fuel.
I only run 89 octane (since 3000 miles since I didn't know that it required this until then, oops).