I finally got a few highway trips done on E85 and thought I'd post the results for anybody doing the same "information gathering" I was doing on this site before I bought my pickup.

1. Towing my little boat (1,500 lb) over the Oregon Coast Range and back = 9.4 mpg (yes I caught some fish and a limit of crab)
2. Freeway trip on a cool day (no AC) at 65-70 = 13.8 mpg
3. State highway trip with a few small towns, using the AC, 55-60 = 13.0 mpg

That gives me a reasonable radius and still be able to get home on the tank of alcohol, but I still think for longer trips I'll just count on refilling with premium as necessary. Doing the math with Oregon fuel prices puts either fuel at about 24-26 cents per highway mile for me so far, with only 3,300 miles on the truck. However, based on what others have reported - I need a tune!

FWIW

 

My wife's Yukon doesn't do any better. If you get a tune but once you put some more miles on it will get a little better.