Basically oil/filter change (6/7K miles), fuel filters (usually annually), coolant change/flush (semi annual), Tranny service (35 to 40K miles). Most of the costs are close to what a gas engine requires, just has a lot more oil capacity, from 12 to 15 qts depending on engine.
I also buy my fuel at a location that sells lots of fuel, truck stops or large service stations. Other than Mexico where fuel quality can be pretty bad at times, the only time I got any bad fuel was in a small country store with fuel pumps in a really rural spot in Wyoming when my 1998 Super Duty was almost new. Water/dirt in fuel....ruined a couple of injectors.