first trip with new truck

Were you towing something? Fuel economy would suggest you had some heavy load?

If unloaded, how was the ride quality?

OP said "FLATBED" right there empty wieght is typically 500-1000 lbs extra tare wieght over a pickup, depending upon what OP speed. Plus wind aerodynamics went down the road depending upon head board, goes it have an over the roof cab guard, or place to put a permanent attach tarp?
If first trip out, most of us know mpg will be on lower side for first 5-10k miles.....
I am surprised it was not 13-15. BUT OP was doing 65mph. Headwind?

Marty

I get 15 mpg with a 2020 3500 with a steel flatbed. Numerous trips from Idaho to North Dakota and all the wind, hills and so forth in the way.

I looked at the OP's profile, and he has a pretty hefty (12K GVWR) bumper pull TT listed there. If he got 10 mpg pulling that trailer at 65 mph then I'd say that's just fine. If he gets 10 mpg running solo I'd think he was driving with the emergency brake on or something.

rjstractor wrote:
I looked at the OP's profile, and he has a pretty hefty (12K GVWR) bumper pull TT listed there. If he got 10 mpg pulling that trailer at 65 mph then I'd say that's just fine. If he gets 10 mpg running solo I'd think he was driving with the emergency brake on or something.

Lol, right?
But leave it to some to not recognize gross order of magnitude of simple things.

just got back from second trip and into service. pulling 18000 lbs of mobile suite from newport tennnessee to alabama.cruise set on 62 got 12.2 average on readout but so far it has been very accurate. about 2mpg better than previous f350 6.0