the best mpgs you'll get will be around 65-70
Just a friendly bit of info... Last year I was in Yellowstone for an entire day doing between 40-50mph. I would have liked to go faster, but the mother in law kept yapping for me to slow down, so that's the speed we went. I was a bit surprised that I pulled 26mpg at this speed. I think our "sweet spot" is much slower than 65-70, but then again, who wants to drive 40mph everywhere? Certainly not me.