Time flies doesn't it? Hard to believe these trucks are getting that old already.

I probably should have mentioned I keep mine on the hot street tune where it's gotten 20 highway. I could probably move it to the tame tune and squeak more but never tried.
Towing I use a tow tune that pumps up the power a tad but still easy on the trans.
And yeah, the pulling power going up the mountains is hilarious. Just use cruise control and it never slows down or even downshifts. Puts my old 79 1 ton with a 454 to shame. That's the sole reason I bought the darn thing.

I pull with a 2007 diesel 3500 dually and it get 12 to 14 towing an enclosed Featherlite and 20 without the trailer. I also have a 2018 dually with 6.2 gas that gets 10 pulling same trailer and up to 16 without the trailer but the power is considerably less than the diesel. When I get in the hills the gas is downshifting seems like a lot to me. I am seriously considering taking the gas 2018 to Hodges and have a car hauler bed installed, maybe then it will ride better. That 18 is the roughest riding damn truck I have ever owned.

I know what you mean. My father has a 2014 3/4 ton gas. It rides like a buck board. His only gets about 14-15 mpg just driving easy highway. Towing his enclosed 24 trailer loaded gets him about 7-8 mpg, it's constantly downshifting and screaming. 6.0 with the 6L80E. He holds up traffic on the mountain grades LOL Even my old 79 454 does better. I can generally pull away from him on the grades, and it gets 10 mpg pulling the enclosed. Neither of them compare to the diesel though.

You are not missing anything Larry, I am having the same results. I have owned several 2500HD Duramax trucks, a 2006,2015,2019,& 2022. Out of all of these the 2019 got the best mileage and 2022 in significantly worse. My 2022 only has about 1,700 miles on it and I haven’t had the chance to tow anything large yet, but both in town and highway MPG is about 2 - 3.5 less than the 2019. I love the 10 speed transmission and all of the tech, but the price of ownership is noticeably higher than it was with the 2019. Without a trailer my 2022 is getting about 13.5 in town and 17.5 on the highway. My highway mileage consists of my weekend trips form PHX to Northern AZ, 150 miles so there are some pretty long grades to climb. If I behaved myself, the old 2019 could deliver 20 mpg on the same highway trip. I don’t regret buying the new truck, just surprised by it inefficiency.

That's the same highway trip that I get my mileage from. My 05 does 20 mpg empty if I keep it at 70-ish. If I drive stupid to keep up with traffic at 85-ish it only drops to the mid 18's for MPG. Same mountain grades I pull the trailers on.

Geez, I have a 2020 GMC HD2500 with 6.6 gas and I love it. It looks like Im getting sbout the same MPG (14 and 17-18 HWY) as the 2022 Duramax. It says my best mileage was 19.6 for 50 miles.

The 6.6 gas engine is totally an upgrade from the previous 6.0.

I've heard good things about the new 6.6. My dad has been contemplating trading his 14 3/4 ton in (6.0) for a 21-22 with the gas 6.6. Still the same 6L80 from what I've read but I think the larger engine has an easier time pulling that truck around and also doesn't use as much rearend gear to do it. I think they come with 3.73's and dad's came with a 4.10

I was hesitant to comment on the thread, because of the age of my truck.

K

2017 HD 2500 CC L5P D-Max, these are typical numbers empty and dragging the box at my usual 75-80. Under ideal conditions I did once see 15.5 with the trailer at 65mph (construction zone), and 28.6 empty with cruise set at 70 mph for 80 miles.
My D-Max is very sensitive to outside air temps and headwinds kill towing milage, and of course leaning on the pedal.

When this truck was new I had the dealer monitoring DEF usage as it seemed to guzzle the stuff while towing, which is 95% of it's usage. Over time that changed and now with 44K on the clock it's not an issue.

Other than recalls for seat belt and block heater it has been trouble free.

Bill W

Do you guys figure mileage the old fashion way rather than rely on that computer screen?

I ask because I've found mine to not be all that accurate. It's actually a little happy.

My screen driving around town always says it's getting about 18 most of the time, probably an average figure, but even when it's just around town for weeks it doesn't change, not to mention that figure isn't even close to actual. Plus the gallons it says it uses is also on the light side.
It generally says I've used 2-3 gallons less than what I actually pump in the tank to fill it.

Basically I don't trust that thing and do the old "gallons pumped vs miles driven" method.