This is usually a blowby issue, and if oil consumption isn't high, usually valve guide seals.
Turbo seal leaks usually result in blue smoke, but can also show up as oil in the intake. You need to check for blowby by disconnecting the hose and seeing how much comes out. Have a care, the hose is BRITTLE with age and heat!
If it is the turbo, plan on a cartridge soon -- once the seals are leaking, the bearings are shot.
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!