Starter is on the left on the M103.

Replace your valve cover gasket and make sure the drain hole is good if there are any signs of oil leakage there.

I'd replace the oil filter, it's a spin-on and there is no reason to suspect that the gasket isn't bad. Worst case there are two there, but usually you dump out the entire crankcase full pretty fast as they won't stay in. I've never heard of the housing leaking, but I can easily imagine a spin-on filter leaking. In fact, the oil change place we use at work has had an entire truck load of bad filters appear -- replaced every single one due to leaking filter seams.

By a Wix filter, Hengst, Mann, or Bosch. If the Bosch is made in India, get one from a different maker.

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!