The 3,000 mile oil changes are acomplete myth. There is no need to do that in any newer vehicle using any modern oil, especially synthetics like Mobil 1, Redline, Amsoil. I have always run 7,500 miles between changes until I moved down this stupid dirt road and now I do 5,000 and I am considering going back to 7,500.
Unless you use the base Quaker Stale/Pennzoil products there is no reason to change every 3,000. It is a waste of your time and resources. Mercedez Benz would not tell you to do something if it was not right. After all, they have a reputation for longevity, why risk it? That is why they recommend Mobil 1. A 10,000 mile change seems reasonable unless your climate has a lot of dust/dirt/dirt roads/severe use.
By the way, Mobil 1 has a new 5W-40 Diesel/Gas oil for trucks and SUVs. Full synthetic and rated for all diesels currently in light trucks including Cummings etc. it is also suitable for diesel tractors. JFYI. J