I just got home from a 2100 mile trip, with 1800 of that towing our fifth wheel. The truck is simply amazing. It stayed in fifth or sixth nearly all the time at highway speeds, only occasionally needing fourth. It'll pull any speed you want on any hill, and going down is even more of a revelation. That big hill on 395 in the Owens Valley, I think called the Sherwin Grade, involved no more than setting the speed I wanted with the exhaust brake in auto and cruising on down without touching my brakes aside from slowing for corners.
I did burn more DEF than I expected but that's not a material cost in the scheme of things. Overall the truck is really impressive. It's a comfortable daily driver/commuter truck, it's great on family trips with the Softopper making for a huge trunk, and driving with the fifth wheel is a non-issue from a driving stress standpoint.
