Could be the chain tensioner, they are known to leak. Up beside the vent line from the valve cover, hard to see from up top.

You could also have a bad head gasket -- if you do, the leak will be from between the head and block at the front or rear.

Oil pressure is higher at high rpm, up to about 65 psi, I think (4 bar).

I don't think you have a front seal leak, but that is also a possiblity. Also, check to make sure the blowby vent tube isn't plugged -- if it is, oil will be forced out a high load as the engine case pressurizes.

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!