Vpierce, now that's an interesting question, my mileage. Usually, I'm at 9.9 mpg according to the Durango gauge. However, on my trip to Alaska and back (11,000) miles I averaged 10.5 mpg and that included a lot of mountain driving. The only difference I can think of is that on my Alaska trip I had a hard Yakima storage box on my roof. Could that box create some kind of air flow away from the flat front of the TT giving me better gas mileage? I'm not an engineer so I don't know but I was continually surprised by the better mileage. On an 11,000 mile trip, the extra half mile per gallon was a welcome surprise. I plan on using the Yakima box now on all longer trips. It is a good place to stow the RVQ which is bulky and gets in the way.