I think we all need to agree that there's a difference between what you CAN get vs. what you USUALLY get for mileage in these trucks.
If I drive empty down the highway at 65mph, I CAN get 20+ mpg out of my 2015 F450. However, I USUALLY get closer to 18-19.
Increase the speed to 80-85mph and the mileage drops to 15-16 mpg
Driving a mix of highway and city with almost 3000lbs in the bed I USUALLY get 15-16 mpg.
That being said, if you look at my all time average which FUELLY does, including all idle time, time stuck in traffic etc. Over the last 10k miles my truck averaged 14.5 mpg.
And yes, I do hand calc the mileage, and it's always within a few 10ths of a MPG of the lie-o-meter, sometimes higher, sometimes lower.



