Today I completed one portion of a test comparing the two. I started by running two full tanks of non-ethanol gas before starting this test. I filled up last week with a tank of non-ethanol and drove fairly conservatively 352 miles for an average mpg of 18.0 actual. The EVIC reported 18.3 mpg, but I never trust it. I always calculate it myself.
Today, I filled up with 19.5 gallons of 10% ethanol gas on top of the remaining non-ethanol. I plan to run two tanks of this gas then start the test again using only 10% ethanol gas. I would prefer to run a few tests to see consistency, but I'm too impatient to wait.
From past experience (in my Dakota) I gained between 0.6 and 1 mpg by switching to the 100% gas. Another observation I noticed was during the summer I average roughly 2 mpg better. I don't know if it's because of the "summer blend" or just due to the temperature. I tend to believe it's based on the temperature and the engine adding less fuel. When the engine sees colder temps it increases the fuel thus increasing the fuel consumption. This is just my opinion though.
I will post my results in a couple weeks.