I didn’t doubt you. That is really good mileage. I would hold onto it as long as you can because others I know aren’t getting better than 18 mpg with their Fords and Rams. I don’t know anyone personally that is driving a newer duramax though.
I have 55,000 on this one now and what I stated is truth. 12 an/change mpg in town playing jockie is my worst with this truck.