Black oil is normal. So are black fingernails from working on anything with diesel oil on them, the carbon won't wash off very well.

Change your filter again, no need to change the oil. All the crud washed loose in the engine will be sitting in the filter -- good place for it, but the filter will plug, if it isn't already, and you will be running unfiltered oil soon.

Happy driving!

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!