Just sent my first xD sample to Blackstone Labs. My 2009 xD had about 17,800 on it at the time, and the oil & filter had about 7,750 miles. As you can see on the form, I was using Mobil-1 0w20 oil. When I change the oil at 20,000 miles, I'll be switching to Red Line 0w20.
By the way, almost 10% of the miles on this OCI (oil change interval) were towing a cargo trailer.
So, to sum it up, my oil at 7,750 miles was in the same condition as most people's oil at 3,700 miles. That's just compared to other cars with the 2ZF-RE engine. This makes two points: 1) Synthetic oil is good. 2) Towing a trailer does not put much stress on the engine.