The only way you could use that much oil and not leak it is through the vac pump or down the valve guides.

Valve guides are the steel (intake) and bronze (exhaust) tubes that the valves go up and down in. There are also rubber seals at the top of the guide to limit the amount of oil that goes down --- oil pours on top from the camshaft, and SOME oil is required (or the valves would sieze in the guides!). If the guides are oversize or worn, or the seals bad or damaged during installation, oil gets sucked down.

Vac pump must vent somewhere, and I though all the 615 engines had a vent line to the intake or air filter housing, but I will check.

Head must come off to fix guides, doesn't for seals.

Peter

__________________
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!