It's a 6.2L gas V8 coupled to a 6R140 6-Speed transmission with the factory 3.73 gearing. It's also an 8-foot bed, so it has the 48-gallon fuel tank.
Loaded for a long cross-country trip, I get about 11mpg on average at 11,500 lbs., which is our GVWR. That can go up or down a bit depending on wind, as drag coefficient is really impacted with any solid-wall truck camper. That said, we live WAY out in the boonies in the mountains of Colorado and it does just fine maintaining speed limits up and over all the passes, cruises at 65-70mph on the highways without issue, and in general performs like a big heavy truck.
