I don't know how similar the programming is between the heavy duty trucks and the light duty trucks, but the computer can be close depending on what you are doing. A tune can change it a lot.

I have a 2015 1/2 ecodiesel, the calculated average shown by the computer is only reflective of something like the last 200 miles driven, it is not a true average over the tank, no matter when you reset the tripodometer.

I towed our boat 200 miles last week and finished the tank empty commuting computer said 23 mpg avg, real average was 19.8 hand calc. If I would have drove hwy first 1/2 then towed second half it would have been the reverse, computer avg would have favored what I did last on the tank(towing) and been low. That is how the 1/2 tons used to be done, I don't know about the hd's or the current production 1/2's either.

Runs better and looks better than mine I'm sure.

My 2020 crew cab power stroke that is not yet broken in(5500 miles) got 20.9mpg last week on the way back from the ranch.

In my half ton ram computer is showing 22-24 typically. Hand calculated it’s always 1.5-2 lower. And since they don’t have to put mileage on heavy duty trucks is why I ask real life numbers. A half ton will do what I need it to just not with any power left. Last time I towed the travel trailer I got 10.5 on the computer. It was bad enough I didn’t even hand calculate that.

Go drive a ford ecoboost. Its got plenty of power on tap.

That's awesome, in mine I get around 12 mpg