My 2019 Ram has a 5.7 Hemi, 3.92 Rear End, and gets 8.0 - 8.5 MPG, towing our camper in Tow/Haul Mode. Our Camper is a 2017 Winnebago Minnie 2500RL weighs around 6400-6500, about 29 feet Hitch to Rear Bumper. I'm using a Curt Equalizer 10,000# Hitch. I have an Airlift Wireless One 50# Combo for my Rear Spring Lift and Stabilizer. Works good, usually have it set at 25#. If it's Windy, I boost it to 30-35# (That's the highest air pressure I've ever had to use to control sway.) When Not towing, I drop the Air Pressure down to the minimum 5#. When Not towing I get around 17 MPG, but have gotten 22 MPG if I behave (55 MPH or so). I have 106,000 miles on my truck.