I'd also replace the valve guide seals on the off chance that new ones will reduce the oil usage some, and while you are doing that, you can check the valve guide clearance.

When you get the spring off, push the valve down off the seat a couple mm and then push sideways -- if you can feel movement of the stem in the guide, it's shot.

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!