Mine turns 2,000 rpm at 75 mph, and I have to have a pretty stiff headwind or a lot of up and down to drop below the low 17 mpg range.
Sounds like you have the 4.30 rear gearing as well. My wife and I took a 120 mile round trip Saturday and averaged 20.7. Never got over 62mph or so as it was a 2 lane rural road. The on board computer was pretty close as it said I averaged 20.4.
