Ram towing mileage

My 2019 Ram limited, 8 spd, 5.7, the best I've ever had mostly freeway driving is 17 mpg, around town it's about 14 mpg, towing my 4000lb RV on the freeway it drops to 10 mpg, with it in "tow haul " as recommended by the owners manual so that's O/D off. It tows like I dream I can do 110 km on the freeway ( about 70 mph ) and still be able to pass slower traffic with ease if needed. 3:92 towing gears. I love the truck, it's my 3rd 5.7 in a Ram. I DIDNT buy it for the gas mileage. I bought because I like and needed a truck. If I need economy I take the wifes v6 Cherokee! Lol.