I have a D4D and I just fill the tank at the end of the day and I talk in litres but I would think what denver has suggested would be at the top end of my gut feeling but naturally as he suggested it depends on how you use it. I have a long tree spear on the front of mine like most Australian dozers do and it makes a lot easier work of pushing them over and I do a lot of clean up raking with the stick rake. I would think if you are more into earthworks pushing a lot of dirt you would be working a lot harder.
Ken