I think everything depends on the engine. I know my w123 300D Turbo hardly uses any oil, and I usually end up filling to just a hair above the full line, my dad's w123 240D uses oil regardless of oil level, my w115 240D uses oil (I suspect this is vacuum pump related though). At the farm I work there are probably about 7 or 8 different diesel engines I'm always checking oil on, both on tractors and pumps, they all seem to use oil differently even though a few of them are the same engine with similar amounts of use.

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1982 300D Turbodiesel, daily driver. Mods so far: Fram 8038 paper filter, 4 brake light mod, Gen II w126 (front) rotors/calipers, boost turned up to 12lbs, non-egr manifolds, water/methanol injection, 4-speed manual
1980 300SD Turbodiesel, project car, nearly ready to hit the street

1974 240D, New paint