I just signed up for this forum. Looks like it has some valuable information.

I wondered what is an acceptable amount of oil to be consumed for a 1971 220D? I have to add a quart about every 500 milres.

The breather hose is loose. Would that cause a noticeable amount of oil to be lost?


Any help is appreciated.

 

Clearly Oil Vapor can come out of the Breather Hose. If it is routed into the Air Intake it will burn in the Engine.
If routed to the ground it becomes an external Leak.

Some Vacuum Pumps have a Tube that goes to the Air Intake. When the Diaphram is ruptured some Oil gets pulled through that Tube.

External leaks due to leaking Seals or Gaskets.

Worn Valve Stems, Valve Stem Guides and Valve Stem Seals can allow Oil into the Engine to be burned or blown out the Exhaust.

Sticking or worn Piston Rings/Enlarged Cylinder Bore keep the Oil from being wiped off of the Cylinder walls properly and some if it burns.

The Fuel Supply/Lift Pump has a tiny O-ring that seals the Rod that pushes the Pump Piston. If that is worn bad enough some have said it sucks the Oil from the inside of the Fuel Injection Pump.
The newer models have Fuel Injection Pumps lubricated by the Engine Oil. The Older Models have only the Oil retained in the Fuel Injection Pump Housing.