It is true, Audi recommends not only a full synthetic, but a "Euro formula" which I believe is a 0w-40. The story is that the motors get gooped up with sludge and the full synthetic keeps that from happening. My son is an Audi fanatic, swears by Mobil 1. He also belives in the 3,000 mile interval.

Now, regarding diesel oil. I knew jack diddly about diesel oil before we got the BMW. So I decided that I would go to talk with the resident experts here, I went up to the Peterbuilt dealer (being some of the most expensive on the road) and talked with the service guys. They said Shell Rotella, straight weight 30......that's it, no either or this or that. The BMW was change at 50 hours or seasonal, but it also had no filter. The Yanmar is pretty goopy inside so I will be using Shell Rotella and changing oil and filter every 10 hours until I can see progress in the oil color. From that point we will go to 100 hours or more likely, seasonal.