I have a 2016 with a 6 speed and 3:55's. I'm on my 3rd camper trailer with this particular truck. My current RV is a 2019 Octane 222 toy hauler. I'm amazed how well this truck handles it. I average around 8.5mpg if I keep the speeds down and my foot light.
We love our 2018 F-150 2.7L Ecoboost. Just towed our Jayco over 800 miles from Texas to Northwest Arkansas. We averaged 10.9 mpg in tow haul mode with cruise control set between 60 and 65 mph while towing. ONLY drove at 65 mph when the roads were real smooth. We also got up to 27 mpg (when not towing) while sight seeing in the Ozark mountains. Great truck and engine.