Recently did a 2100 mile trip across Texas. MPG varied greatly depending on speed and conditions. 2016 F150 FX4, supercab with 2.7 L ecoboost engine, with a 2019 FWC Hawk
Worse mileage was 11 mpg, driving into a strong headwind doing 75mph. The truck downshifted into 5th speed often, but I was in a hurry and west texas speed limit is 80 mph and I was paying less than $2 a gallon for unleaded, so what the heck. Bought fuel as low as $1.56 a gallon.
Best was 16 mpg driving 60 mph, on back roads no wind, pretty flat.
I have decided it's worth keeping around 65 mph and then I get around 14.5 to 15 mpg, which is fine.