seems to defy the laws of physics
10% of the fuel has 67% of the energy content and you claim that much degradation?
The alcohol changes the way the computer and sensors interact. Although just 10% of the mix, the programming in the computers is optomized for 100% gasoline, and does not give good performance (gas mileage) with gasahol.
The older carbureted engines are affected the least, the newer, smaller computer controlled engines really take a hit.
I know of several Hondas that are suffering greater than 25% reduction in real world fuel mileage on E10 pump gas. The mileage goes back to normal after running 2 tanks of real gas through them (boat gas, no alcohol). Checked several times and is repeatable.
Have worked on several dozen engines lately with similar results, but non quite as bad as that 2.2 Honda.