My '13 D22 2.5 30,000klm gets roughly 700klm to a tank. That's with, Steel bulbar, spotties, winch, canopy, roof racks, fridge in back and a lot of camping gear. From stock with no mods. I could get 750+klm to a tank driving like a granny.
I do change gears at the 2250rpm mark though. Except...