I used it for the month of May. I tow a trailer for my business and with E85 I was getting about 290 miles to the full tank, as opposed to ~360 with 87 Octane. Granted, the month I decided to use nothing but E85 turned out to be a hectic month for me workwise at quite a bit of distance from my home office, I ended up putting 3,480 miles on my Yukon which cost me $1,060.49 @ an average of $3.399 a gallon that month. I have not had an identical month by comparison. I used 87 Octane for my second busiest driving month which was 2,542 miles in June, and for that month I spent $721.32. Just for entertainment, I took my amount of miles driven in May and guesstimated what it WOULD have cost me to run 87 Octane for that period. Hope these help a little, I am a firm NON-believer of E85, sure the money goes to our farmers, but I am paying even more for a product that doesn't even face taxation for importation. I think that if it is a homegrown product the difference and impact should be higher than what I have experienced. By the way, since I haven't used FlexFuel since May, I have seen less and less people using that pump at the local gas station, it's price has reached $3.939 a gallon while regular gas was $3.799 a gallon.
E85 May
3,480 miles/month
~26 gal/tank
~290 miles/tank
$3.399 avg/gal
$1,060.49 a month
87 Octane(May est.)
3,480 miles/month
~26 gal/tank
~360 miles/tank
$3.929 avg/gal
$987.49 a month
87 Octane June
2,542 miles/month
~26 gal/tank
~360 miles/tank
$3.929 avg/gal
$721.32 a month
Legal Disclaimer: I may be off by a few dollars, each fillup ranged from 24-25 gallons roughly, I never really did put in 26 gallons, though GM claims that is my tank capacity. Prices per gallons were averaged for the different amounts I payed throughout the month. Miles per tank were also averaged as there were different amounts from each fillup to the next. So please no one breathing down my neck if these figures do not match yours, thanks.