FWIW, The service manager at my dealership said that most of the break in occurs within the first 500 miles on the newer engines. He went so far as to say that it's during this period that the longevity of the engine is largely determined. Providing for regular maintenance, of course. I did the first oil change, to Mobil 1 on my y2k ML at 400 miles, and the second one at 4,000 miles.

...tracy