2024 3500 regular cab 4x4 6.6 gasser.
My absolute worst was when it was new with maybe 1,000 miles on it on a trip, on a 80mph interstate, going 82mph, with a almost dead headwind enough that the wind turbines were making good electric power. So that tank got about 12mpg, hand calculated, winter so the temps were around 15f. Also, that was 10% ethanol fuel 87. No choice up north hear. Best tank to tank so far, with the same type fuel is 16.5mpg, Thats rural roads, calm one day, windy the next, hand calculated. The dash is very close to hand calculated. 11,200 miles on it today, bought 1/23/23.
A person has to come to reality, that the L8T 6.6 gasser is made to work, and like it, alllll day long, every day, for those that dont want or need a diesel but need more than a half ton. Then be a car, that isnt the best on fuel economy, but fun to drive.
I am retired and full time rv it, its my home. I took last winter off, but am back at it with a new to me 5ver and my new cheby. I am coming from a 2500 diesel after 8 years of that. The simplicity of the gasser is refreshing, with its simplicity. All winter hear, way up north in MN, diesel was a solid $1.35 more a gallon, and now its .50-.60 cents more a gallon. So the cost tank to tank is a wash or better, for me and my driving needs and area. I have only towed my 10,000lbs 5ver for 70 miles so far, as it will sit till fall then head south. If i get 6mpg worst ill be happy, if i get 8 mpg or more, that will be a treat. my 5ver is tall with the front added AC unit, so lots of air to catch.