@Rusty-Vandura Highway mpg on a truck is so dependent on load and speed, but that doesn't sound unreasonable, especially in an older, heavier truck. The F-150 dropped around 700lbs of curb weight (+/-, depending on configuration) when the body went aluminum in 2015ish. At work we have the 3.5 Ecoboost in our 2022 Expedition and 2023 F-150 (crew cab/super short bed). At 75mph, the expedition returns around 19mpg, and the F-150 can do 20 or 21mpg in pure highway. Both of these trucks are on somewhat up sized, 10-ply/Load E all terrain tires that are definitely impacting fuel economy.
For comparison, we also have a 2021 F-150 with the 2.7 Ecoboost that returns around 17mpg on the highway, but that truck also has utility shell on the back that's 6 inches taller than the cab, plus the rack on top of that. It's got a fair bit of extra weight and aero drag. Our 2016 F-160 with the 5.0 typically does around 13-14mpg at 75mph, and it has similar utility shell, rack, and lot of extra weight on it at all times. Also both on 33ish inch, 10 ply all terrain tires.
My new 2024 F-250 with the 7.3l gas motor returns a significantly better than expected 11ish mpg on the highway. It also currently has a 2" lift, 34.5" off-road tires, some armor on the underbody and a beefy grill guard out in the wind up front. The utility shell is still on order, so I expect highway mileage to drop a few more mpg once the truck is fully upfitted and loaded out.
