Just towed my 29ft travel trailer across Canada from Eastern Ontario to Vancouver Island with my 2017 1500 Sport. Trailer dry weight is 4900lbs and maxes out at 6900lbs, but it was probably closer to 6000 for the trip. Used WDH and sway control the entire time.
Pulled fairly well through the Rockies, and averaged 23 L/100km (10.2 mpg) for the trip there and back.
This was mostly on 87 fuel.. I started the trip with 89 and 91 and noticed no difference in power or fuel economy when one station had no higher octane fuel, so for the last 3/4 of the trip I only used 87.