Mobil 1 15W-50 is CF rated, making it appropriate for light use diesel engines (read any passenger car). Furthermore, it and Mobil 1 0W-40 are specifically on Mercedes' schedule of approved motor oils.

You can use extended change intervals with Mobil 1 provided that you get the oil out before the additive package is depleted or the soot levels are too high. You can have oil analysis done to determine what mileage is right for you. I've settled in on 7500 miles, which actually is probably a couple thousand miles early.

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Tjohn

82 300 SD
77 450 SL (gone)