Well, just did a 5 day, 4 night trip to the heart of Ozark country, canoeing on the North Fork of the White River, then going to Johnson's Shut-Ins , Taum Sauk Mountain, Elephant Rocks...anyway, this country is quite hilly and narrow. The place i camped on the N. Fork required a bit of clearance and the XD-Oliver combination was right on task...just doing great. The Oliver's narrower footprint than many boxier RV's was quite helpful also. So, the mileage question..My estimated average load was ~6200 (guess), I pulled ~ 95% of the time, and the topography was windy and hilly (to very hilly) ~90% of the time (we were driving some back, back little roads much of the time). The A/C was on 99% of the time. and i averaged 12.6 mpg. i'm gonna say i'm quite happy w/ that.