Why go slow!?! I drove up and back from Phoenix to our place in Flagstaff last week in my M3, windows up, A/C on. Door-to-door it's 175 miles, with only about 10 miles of the drive not on the freeway. You gain about 6,000 feet in elevation going to Flag, total climb with the ups and downs is probably around 8,000 feet.
I made one stop going up, my average speed overall was 67.1 mph, and I got 24.5 mpg. Coming back, I averaged 70.8 mph and got 29.7 mpg. I'll bet the Boxster with the roof up would have beaten these averages.
If I'd done as Perfectlap did, I probably would have gotten a few more MPG, but a much lower FPG
