So...I purchase my third MB diesel, a pristine 1984 300 SD Turbodiesel with 117,000 miles...I drive it home, am astounded at the way the thing runs on the interstate (that's the freeway to you Yankees)....I am in love.

The very next morning I go out to the garage, open the hood and check the oil...right?

Horror of horrors, the official MB dipstick says the thing is at least a quart overfull.

I race to the shop, drain a quart and go on about my business.

But I'm still worried. So I read, and read and read....including the oil checking odyssey of the much-revered Professor Booth ("drive to McDonald's, then back home, measure the ambient temperature, calculate the impact of global warning.....etc, etc, etc")

And what I discover is that there is no way to accurately check the oil in this damn car with the dipstick Mercedes supplies with the car.

The original owner's manual says 7.9 US quarts, but nowhere does it say that, on start up, at least a quart goes into the oil filter, and that there is at least a quart that lives forever in the oil cooler.

What the owner's manual is telling you is that the total system capacity is 7.9 quarts with filter.

It does not say you should refill on changes with seven quarts, or slightly less.

Ultimately, the short answer here is that Mercedes dipstick is too long to be of any use unless you scribe your own marks so you can check the oil in your 617 when it is dead cold, which is the only way to get a consistently accurate oil level check for any car except one of the air cooled Porsche's.

I notice Mercedes came up with a novel solution in the later models. They eliminated the dipstick and replaced it with an idiot light.

Would it not have been simpler to just use a shorter dipstick?

Other opinions would be welcome.

I hope you have right dipstick.I have no trouble with mine.Drain a little oil till level.Drive around and recheck.Sometime the lift pump,can pump diesel into the oil.Watch for rising oil.If so change lift pump.

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1999 w140, quit voting to old, and to old to fight, a god damned veteran

I hear what you are saying, but I have checked the cold oil level in four other 300 SD Turbodiesels in the last week, and they all indicate approximately one quart over full.

I don't smell any diesel in the oil....fwiw, the dipstick on mine has a white pull ring, but others with orange, red, etc were the same length, and showed a quart over in their respective cars.

I would love the solution to be that I have the wrong dipstick, but I am afraid it ain't so.

How did you reach the conclusion that the existing dipstick markings are incorrect? Or that it is "too long?" (Hopefully, you did something more scientific than the "random survey.")

If your oil level increases substantially when the engine is "cold," it could be that your oil filter housing is draining, which likely means that the o-rings on the oil filter cover pipe need to be renewed.

I suspect that the problem lies entirely with faulty logic, and not with the oil dipstick. The fact that a random survey found other overfilled engines provides no data whatsoever about the accuracy of a particular dipstick.

Actually, we "Yankees" call it the highway... freeway is for Californians.

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"Senior Luna, your sense of humor is still loco... but we love it, anyway." -rickymay ____ "Your sense of humor is still loco... " -MBeige ____ "Señor Luna, your sense of humor is quite järjetön" -Delibes

1982 300SD -- 211k, Texas car, tranny issues ____ 1979 240D 4-speed 234k -- turbo and tuned IP, third world taxi hot rod

2 Samuel 12:13: "David said to Nathan, “I have sinned against the Lord.” And Nathan said to David, “The Lord also has put away your sin; you shall not die."

I'm in Tennessee but I miss my Freeways.
I've never paid attention to 7.9 quarts I dump two gallons in and run it.its then at the 2nd notch meaning full. From then on I run it between the notches

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1999 w140, quit voting to old, and to old to fight, a god damned veteran

If you'll read the engine oil when it is dead cold first thing in the morning, the oil level will read maybe 1 cm higher than max, ONLY when the oil reads exactly at max when at operating temperature and level ground. What the manual doesn't tell you is that this extra oil is in circulation when the engine is at operating temperature.

So naturally the manual states to check engine oil when at operating temp. This is for a W123 but the principle is the same on the W126:



Since you already drained a quart, run it to operating temperature and check the oil level. Now it will show it is a quart low.

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"If your oil level increases substantially when the engine is "cold," it could be that your oil filter housing is draining, which likely means that the o-rings on the oil filter cover pipe need to be renewed."

AH HA!!!!!!

In all the stuff I have read, in all the emails I have sent to "experts", nobody has mentioned this.

Yes, the oil does drain from the oil filter housing into the pan when the engine is not running.

This is great news....I will replace the o-rings.

A poor quality oil filter element could also allow the oil filter housing to drain.

Doubt the oil filter is the culprit....came from a very good source, excellent brand