My 2022 Ram 2500 Cummins got a new PCM, and the MPG changed. 

Louisiana I get 25-27 @ 60 mpg 2022 3500 diesel long horn mega

I have a 2022, 2500 big horn and driving up and down and across the mountains in south western PA, in the summer months, I’m getting 17.6 mpg. On the highway running 70-72 I’m averages 22-23 mpg.

There are so many variables that can affect it. The only way to know for sure is to do two identical runs at the same speed. Higher altitudes have a great impact too as the air is less dense. But for sure speed at the higher end has a huge impact on mpg. Usually the optimum speed is the lowest speed you can achieve in top gear but that is not always practical. If you can resist going too fast, say only 65mph, you will see a huge difference in mpg. It exponentially uses more fuel above that.

I went from AZ to MI and back in September. My overall was 20.5. Best was 22. I own a 2022 2500 Ram with the Diesel.

I used to get over 20 mpg in my 2500 Chevy Duramax unloaded highway driving. Then the DEF Tank Assembly went bad. After more than three months, they “fixed” it. Now it gets about 16 mpg unloaded. I see the same 5-6 mpg drop when towing too. So, you should feel lucky.

Adorable girl in the back seat. No question she's your child...similar face!

my truck going 85mph with a hemi and 4.10 gears the fuel is 9.5 mpg and at 65 mph is 12 mpg

Don't go off the computers mpg. They are often not accurate. You have to do the top off and trip reset method to get the real number. Mpg is the most wrongly measured thing all over the internet on forums, groups and RU-vid because people go off the computer.

I can’t break 16 mph on my 22 Ram on 35s. My 2020 with the same setup I could get 20.