Significant difference in oil level when checking hot or cold
 

Quick question..

When I check the oil level in my OM616 first thing in the morning it is at the low point on the dip stick (or a tad below it).

Once the motor is warmed up, and I mean full operating temp for a bit so that the oil is hot it will read around the halfway mark on the dipstick.

How is this possible? Wouldn't common sense dictate that the oil level would be less? Does oil really expand that much?

Reason I ask is that I once added oil based off the cold reading and ended up with an overfilled engine that I had to drain off.

On the other side I don't want to be driving around with a low oil level.

/End neurotic ranting. thanks!

The oil cooler has a thermostat that opens and releases extra oil from the oil cooler making the dipstick reading correct when hot.

My general rule is that if you see oil on the dipstick when it is cold, you have enough to run the car. If you are at operating temperature and it is low, consider that to be the correct reading, and add as needed.

Dkr.

Ok this makes perfect sense. Thank you!

I was wondering this same thing! I haven’t seen any oil leaks and was worried when measuring cold because it looked just at “even,” when I recall checking warm after oil change it was firmly on “high” side of even. Thanks!!


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Except he oil cooler always has the same amount of oil in it at all times (even when doing oil changes it never drains completely). The thermostat valve only opens the pressure supply end, the return from the cooler is always open to the oil filter housing.

hmm not sure what to say then. I just confirmed again, check the oil stone cold and it registered right at the low mark on the dipstick, took the car out and drive it enough for the oil to get hot (idle oil pressure around 1.75 bar) and after checking the level its a hair under the middle mark on the dipstick.

Do 616s even have an oil cooler?

Mine reads about the same cold as it does hot after sitting 20-30min to let all the oil return to the pan.

mine does, located next to the rad, front driver side.

Interesting. My 1980 240D does not. Guess my input may not be that relevant here.

My car shows slightly LESS when hot compared to cold, more oil sitting in the filter canister and more oil retained in the head. Let it sit for 15 mins or so and the reading is the same as when cold. Oil does expand when hot, but it shouldn't expand that much...

My 1981 240D has that same oil cooler next to the radiator.


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AFIK, you should have one unless someone deleted it.

Dkr.

I’m familiar with what you’re talking about, my 300TD had it. You had me second guessing so I went out and looked:

https://uploads.tapatalk-cdn.com/201...fb9032e7ac.jpg

Interesting. Any idea if that is stock? I have seen oil coolers on 240Ds, but there aren't as many as 300Ds, so I wonder if the older ones may have not had it or it was an add-on item.

Dkr.

Any 240D or 220D I've had that did not have airconditioning, did not have an oil cooler.

He may have a car without AC. That's my personal experience.

To the OP, I find I need to wait a significant amount of time when hot to check the oil after shutting down. Checking the oil during a fuel fill up may not give it enough time to fully drain back.