With my old MKS as well as my new Conti, I have found that speed makes a huge difference. Driven in the 60 MPH range, my MKS would get close to 30 MPG but at 75-80 it would be closer to 24-25.
Regarding E85, my wife's naturally aspirated Taurus is a flex fuel vehicle but E85 drops the mileage pretty dramatically - at least 4 MPG. On the flip side, I have been running one of Brad's E-tunes in my Continental and using approximately an E40 blend and my fuel mileage is just as good or better as when I run E10. Apparently, the advanced timing is making up for typical characteristics of poorer mileage with Ethanol.