I don't get the need to let them warm up before driving, driving them will warm them up faster. Let them get some temp in them before hammering down maybe I don't see why you shouldn't start and drive.

I have owned, or have had diesel work vehicles from the big three. I would say none of them get the mileage you see on the internet, and none of them are perfect. But they all have enough power to drag 40' 5th wheel travel trailers without wheels under them lol.