I got 15mpg combined non towing and 9mpg towing a 7800lbs tt. Not to rain on your parade but it was the worst truck I have ever owned and horrible for towing. It was in the shop at least once a month, 4 transmissions, rust, electrical problems....the list goes on. Needless to say I didn’t keep it long.
Search the 1-2 shift and read on about the complaints. The gear spacing is terrible. Mine was always bogged down even non towing because it always wanted to start out in 3rd gear. You’d have to floor it to accelerate at all but then it would drop 2 gears and lose control. Even worse when towing. Several times I couldn’t get it to accelerate out of 1st gear on hills.
Get a 6.4l with 4.10s and you’ll be much happier. It has cylinder deactivation for better mileage as well.