So I decided to let the gauge dictate the speed I drove (within reason) and found that the faster I went, the better the MPG. I didn't test this past 80mph, although traffic was going faster at times. Most of the stretch was highway, but there was a little city and stop and go also. Based on what I got at the pump. I think I've calibrated my gauge too low, but the next step up seemed too high... more testing needed.