Understood, I do try to keep measurement methods accurate. I guess "horrible" is a relative term, it is after all a 3/4-ton truck and has 33" tires with fairly aggressive all-terrain tread pattern. Based on what most people over at Ramchargercentral tend to get on their old Dodge trucks though I think it should be more like 12-14 MPG. I know it also doesn't help I have a hard time keeping it below 70 mph on the freeway, need to work on being patient lol...
Makes sense. I assumed an A-body. That loud noise you hear from knobby tires is energy being wasted. Shift to "N" and see how fast it slows from 65 mph. If it keeps decelerating the same after 40 mph, the drag is more from the tires than aero.