Just ran this tonight on my supercharged m3... 3 gallons E85 and topped it off w/ 91. Initial impressions are that it does run a bit stronger. Temps outside were 95*, and the car pulled nicely.
Oil temps rose just slightly above the center line. I was pushing the car and keeping the RPMs around 3500-4500K around 40-50mph while "cooling down" for a couple minutes in-between pulls.
I will perhaps need to pick up this bluetooth tool some of you guys are talking about. Perhaps someone could link me to it. I obviously have a OBD-2 cable, so if there is a better program out there to log, it'd be appreciated to clue me in.
Not very scientific so far, but it's all I have to contribute. I'll gladly post logs once I figure out how to do that.