Just had an image of a 90 year old in an HD ram pulling into church. Im sure she'd need jesus to get down from that truck
LOL... he / she would be the coolest 90 years old !!
Regardless, my old 2005 RAM 3500 4x4 dually Diesel (the silver one on the left of my avatar picture) when it was new it consumed about 14 to 15 miles per gallons, it wasn't before it reached around 80,000 miles that the mileage improved to a consistent 16 to 17.5 mpg !!
And same goes for the oil consumption as well: first 10,000 miles it was about a half quart low, then gradually improved to
zero oil loss at around 100,000 miles (with 10,000 miles oil change intervals).
Fuel consumption from 100,000 to 230,000 miles gradually decreased until the injectors failed. I then replace all 6 injectors (got them from "Injectors Direct") including the CP3 pump and instantly got right back to 17.5 mpg.
Oil consumption increased from 100,000 miles to today's 350,000 miles, of course I changed the front main seal at around 250,000 miles and recently the rear main seal during my last clutch replacement at 320,000 miles.
Now, at 350,000 miles, with small oil seepage(s) here and there and considering the pistons rings wear: the engine uses about 1 quart of oil X 10,000 miles. Not bad for that kind of mileage !!

The truck is used on a daily basis to carry construction materials, since the day it came off the dealer lot.