I just got back from a 2200 mile trip - family of four plus camping equipment, three mountain ranges while traveling through Idaho and Montana at 75 MPH.

20.5 MPG

On a 2009 SCREW, 5.4, 3.31 rear end

Best truck I have ever owned and it is getting better gas mileage than I expected.

 

That offsets my trip--2800 miles, family of three, towing a 3500lb (empty) camper loaded with all our stuff and probably on average about 20-30 gallons of water, grey water, and black water traveling across OH, NY, MA, a small part of NH, ME and PA on the way back at about 72. About 13MPG, and that was probably helped by the times we weren't towing. But about what I expected. It performed very well, when I didn't forget to push the tow/haul button. I wish it would come on automatically when the IBC detects the trailer. I'd realize on the first hill that it wasn't engaged because when it is engaged and you start up a big hill, the trans kicks down immediately.

 

That 3.31 rear end really helps... best I've gotten with my 3.73 is 18.1 MPG.

 

I'm averaging 18-19 according to my display, which is about 75% highway miles.

Anyone figured actual mileage to compare to the average MPG that displays?

I did a while back when I filled with half a tank remaining. The average that was being displayed showed 17.6 and my actual mileage figured (miles driven/gallons to fill) was 16.7. Haven't checked it again, but my first comparison showed slightly less than what is being displayed as average. Not sure if this is a fair comparison or not though.