Driving 55mph? (Is it the most efficient speed?)

[comptiger5000]

My Jeep seems to do best between 50 and 60mph (about 26-28 mpg on the instant display at steady speed on flat ground). The mpg doesn't really change much in this range. It's not quite as good from 40 - 50, as it's a little low in the RPMs, and its harder to drive it smoothly at that speed on most roads around here. Around 30, it's pretty good, given good coasting conditions. Above 60, the bad aerodynamics start to take their toll.