I have a stock height, stock tire height, 3.73 geared, 4x4 03 Excursion.
We’ve owned it for 9 years, and we have put 195,000 miles on it in that time. Started out bone stock, currently is 550-600 hp. I have EVERY SINGLE fuelup written down (date, miles, $ per gallon, and gallons) since we’ve owned it.
It has only gotten into the 18 mpg range on 4 tankfuls of fuel in the entire time we’ve owned it.
I did the same record keeping on an 07 LBZ Duramax that I bought new and put 88,500 miles on. It got 18.?? on 3 tankfuls the entire time I owned it also.
I call bs anytime someone claims they can consistently get 20+ mpg on and 3/4 or 1 ton diesel pickup.