Use full synthetic (Mobil 1 is good, there are others). MB does NOT recommend 10W30 or 5W30 oils, use either the 0W40 or 5W50 truck and SUV oil and you will be fine.

You will need to do an extra filter change after 1000 miles or so when switching to synthetic oil from dino oil -- all the varnish and stuck down sludge (and there will be quite a bit) will dissolve and all the solids will end up in the filter, cloggin it.

You can easily run 6000 mile intervals with synthetics, more if you have an oil analysis done and change when it needs it.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!