Most half tons towing RVs are limited to their payload or receiver ratings, not tow ratings. All gas engines get about the same fuel economy towing any high walled RV, 8-10mpg. It isn't the weight as much as poor aerodynamics of pulling two vertical sheets of plywood through the air at 65mph. Ecoboost is no different when working. It's the unloaded times when it can be better than V8s. Without details, I generally recommend under 6k dry for a travel trailer and the more capable half tons.
I highly recommend the Ecoboost for towing. It has all 420ft-lb of torque at 2000rpm, right where we tend to tow anyway. Owners report towing in 6th and 5th great, with very few downshifts required to 4th unlike some competitors. Also, forced induction engines loose less power at altitude than naturally aspirated.
