The gasket leak is normal, as is a slight ooze at the bottom of the intake runners (although that usually turns into a leak, meaning time to replace the gasket). You can put in a new gasket, should fix it for the time being, but they usually show some black oil there.

Oil in the turbo is normal -- the blowby is routed to the intake in front of the turbo, and ALL diesels have some at highways speed.

Mobil 15W-50 is fine, it's what I use when I can find it. These days, it's Mobil 1 Truck and SUV oil (aka Delvac 1) which is probably better, since it has better compression engine ratings and holds more soot.

If the engine has been run on dino oil up to now, change the oil filter and top up the oil at about 1000 miles -- all the varnish in the engine will dissolve and any hard stuff will end up in the filter, sometimes plugging it. Won't be a problem with good maintenance, but filters are cheap and the job is easy.

The pressure valve holder is what the injection lines screw into on the IP, but I'd have the injectors checked first. They do usually run 250,000 miles or more without problems, though.

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!