Halfway through tank #3, I got the Check Engine Light. My Scanguage II says it's P2195, which is for one of the O2 sensors, lean condition.
I tried to clear it, but my scanguage wouldn't clear it.
I'll run through the rest of this tank and fill up with 87 octane to see if it clears. If it does, it would seem that this car is much more sensitive to E85 than my Saab was (which wouldn't get the code until 40% ethanol).
Or... this is just a car with 153k miles and the O2 sensor went.
I'll keep you posted.