Ram towing mileage

2020 Laramie 5.7 with E-torque, 8spd, 20" wheels, and 3.55 gears(I think). I get 17/18 around town and 18-20 on the highway depending how deep my foot is in it. Recently towed my daughter's CRV back to Wisconsin from Waco, TX and averaged 12.5-14.5 mpg depending on whether we were in the hills or not. Truck acted like it didn't even know the car was back there. Got a solid 1.5 mpg better while running non-ethanol gas. I have the 33 gal tank and can get nearly 600 miles without stopping on long trips, but my bladder and butt can only handle about 400.