Finally Mobil is making a synthetic motor oil for diesels. Mobil 1 5w-40 should be on the shelves in your local auto parts dealer soon, if not already.
There is Mobil Delvac 1 5W-40 and Mobil 1 Turbo Diesel Truck 5W-40. Near as I can tell they are about the same but since I used the Delvac 1 before the Mobil 1 came out I have stuck with it. The Mobil 1 turbo truck has been on the market for some time.