I rented this exact truck a few weeks ago to pick up a car.

2012 Crew Cab, 2500, Hemi 4x4 with factory tow package.

Towing an 18' open trailer (empty) the truck got about 16mpg according to the trip computer.

Towing it with a car on the back, mileage dropped to about 12-13mpg

This was over a 600 mile round trip on relatively level ground.

There is lots of power, IMHO the truck struggles a bit in 6th gear at less than 67mph with a loaded trailer. Either drop a gear, or drive faster - both improved the mileage.

But overall, a nice combo to tow with.