W115 OM616 1974 240D

Only had it a couple weeks. When I bought it the dipstick was halfway between the marks, and over the last couple weeks it went down a little below half (leaves little drips on the driveway, and smokes a bit when cold) so I figured, "Hey, might as well top her off..."

I added about half a quart and brought the dipstick almost up to the top mark. It now seems like she is smoking heavily when accelerating, regardless of temperature. She used to smoke a bit when cold and when pulling away from a stop, or downshifting, but not really that bad. But after the top-off she now leaves a pretty heavy cloud (grey?) every time I pull away, or floor it in 2nd.

Been reading the threads about smoke and overfill, and it seems like I must have filled her too much, and that maybe halfway on the dipstick is just about perfect... So I guess my real question is:

Should I immediately drain off a little oil, so as not to damage anything, or risk a runaway? Or should I just let the old gal do her thing and burn up whatever seems excessive. I ask with some urgency, as I was planning on making a 300 mile round trip this weekend, including some substantial climbs up into the mountains.

Bonus Question:

Do the top and bottom marks on the dipstick actually correspond to any numerical values, or is this something I'll just kind of get a feel for as I do oil changes?

Thanks!

Yeah, I defiitley overfilled it... I just checked the dipstick on the dead cold engine and it's way higher than it was when I filled it warm! I guess quite a bit can be reserved in the engine. Dang. Well, I'm gonna drain off a little bit just to be safe. With all the blowby I already have on this thing, it can't be good.

Rule #1. The only accurate oil level reading is after the vehicle sets over night.

Rule #2. If the engine has run in the past hour the oil dipstick is false - wrong = inaccurate by 0.5 - 1.25 US quarts.

Rule #3. The engine is safer running 0.5 - 1.0 US quarts low, than to ever risk going above the full level.

Rule #4. If in doubt refer to Rule #1, #2, and #3.


For more exhaustive information on this topic, please read the following threads.

Best oil level for a Diesel engine

Run away diesel, why does it happen?
Run away diesel, why does it happen? - PeachParts Mercedes ShopForum

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1985 300SD
1983 300D
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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

I believe a 74 616 has a diaphragm in the vacuum pump, which, if it fails, allows oil to be drawn into the intake manifold. I also believe that a failed diaphragm in the vacuum pump will cause the same thing.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

You said vacuum pump twice, you didn't mean injection pump for one of them did you? I've read about there being a diaphragm in the injection pump for the shutoff or idle control or something, and if its leaking it can also cause oil consumption

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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