I would belive a car with a Kompressor, which I think is what you have will get the oil darker faster than most cars. I think they would be more like a deisel having more blow by due to high compression or in the case of the kompressor boost. I havent worked on one of these so I cant be sure. But I have changed the oil on many MB diesels and after starting the car once you usually couldent even tell the oil was changed by the color.

I would feel the oil with my fingers. If it feels like it has reasonable viscosity it should be OK. But if you are in doubt, have it changed there the next time and check it imidiatly after the oil change. Then check agian after about the same milage you have now and see how the oil reacts. If it turns black in the same amount of time then they probably did it right.

John Roncallo