I learned on the internet that "About 1.68 litres of ethanol would have the same energy as a litre of diesel oil." I still need to get the number for gasoline, but assuming it is close to diesel, I compute that 1 gallon of ethanol has about the same energy as 0.6 gallons of gasoline. Therefore, 10 gallons of 10% ethanol blended gasoline has about the same energy as 9.6 gallons of gasoline. That would explain most of my mileage loss when running the blended stuff (about 7% worse gas mileage).
I really want to find out the difference in CO2 tailpipe output when traveling 100 miles on 10% blend versus the pure stuff. I have a sneaky feeling that the ethanol increases CO2 per mile, hence contributes greater to GLOBAL WARMING