You'd be surprised how little oil the engine needs to run. On a project car I changed the oil and didnt have a new filter seal so I put it together anyway. Got back from going to subway, decded to check and see if I got the oil level just right. I pulled the dipstick out and found it dry. So i put it back in, pulled it out, nothing! But it still had 2+ bar at idle!

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1981 300SD 512k OM603