I had read several years ago that Mobil 1 syn oil would have qualified for the diesel API rating, but Mobil chose not to have it certified for the diesel. I've heard it's quite costly to API certify motor oil. So, I wouldn't worry about it. This time....

Recommending a fuel additive is sure to bring some debate. GM "approves" of Stanadyne & Racor brand fuel additives because of their water demulsifying nature. However, I've used them and others in my GM diesels. I recommend using a mainstream fuel additive that can be found in your local area, that advertises a cetane improver, injector cleaner and that adds additional fuel lubricity. Except for the offbeat stuff, it's hard to go wrong with just about any commercial diesel fuel additive that you might find discussed here in TDP.

Jim