Oil level reading on dipstick too high?

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Kanis

New Member
Joined
Nov 6, 2023
Messages
9
Location
Norway
Car
W205 C300et (2020)

Good evening!

I recently aquired a used mercedes C300e (estate) (year 2020) with 34.000km on the clock. Today i decided to check the oil level and discovered that it was too high, as far as i could see. From the attached image you can see that the level is almost 10mm above the maximum mark. I found this odd, because the oil level was presumably checked by an independant workshop before the car was sold, and they said it was within norm. And just for the record, the seller is a reputable company. When measuring the oil I have followed the exact procedure described in the manuel. I ran the car to operating tempereature (90 celcius), turned off the engine, waited for 5-6 min, pulled out the dipstick and wiped it, put it iback in again and waited for 3 sec, pulled it back out and read the oil level. Did several readings, with the same result every time. The car stood in a parking garage with a level floor.

From what i understand, 10mm above max mark would indicate aprox 0,5 litres of excessive oil. How critical is this for the engine? I think it has driven almost 1000-1500km since the oil was changed. Maybe even more...So far the car is running fine, without any wierd noises, smoke, or oil leaks.

And does anyone here know if this spesific model will notify the driver if the engine has too much oil (on the intrument cluster)? The user manual states that there is indeed such a warning, but it notes that its only for certain engine models, and there is no mention of which engines this relates to spesifically. I believe my car has the M274 engine, and since it has a dipstick, i would assume this car doesn´t show the "high oil level" warning. At least i havent seen this warning.

I love the car, but im really worried that the engine and/or catalytic converter may already have suffered damage/wear due to this overfill
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Do you know when the oil was last changed or topped up?

Here’s what I’d do. Tell the seller ASAP and ask that they drain some from the tank, or better still do a fresh oil change.

If that’s not practical (eg long distance£ tell the seller ASAP and do the above yourself, or ask a local mechanic/workshop.

Put it all in writing with photo evidence in case the car develops a related fault sone time down the line.

Then get on and enjoy your new car 👍🏻
 
Half a litre too much oil isn't great, obviously, and yes too much oil isn't good, and yes you should syphon some out - but too much oil in a petrol engine isn't as a big a problem as it is in Diesel engines.

I suggest that you drive the car normally and arrange to get some oil syphoned out at the earliest opportunity. I wouldn't treat this as an urgent matter.
 
As said, not a huge issue, I very much doubt that it will have caused an issue. Just have 500ml - 1 litre sucked out - it will take 5 minutes to do.
 
Do you know when the oil was last changed or topped up?

Here’s what I’d do. Tell the seller ASAP and ask that they drain some from the tank, or better still do a fresh oil change.

If that’s not practical (eg long distance£ tell the seller ASAP and do the above yourself, or ask a local mechanic/workshop.

Put it all in writing with photo evidence in case the car develops a related fault sone time down the line.

Then get on and enjoy your new car

Looks like it was serviced last time at the end of May. And its driven 2000km since then. With probably 1/3 of that on pure electricity.

Yea i have already informed the salesman about the issue and sent him a photo. Still worries me though, because when/if something happens in the future, i bet it will be very hard to prove that the overfill is the root cause...

Will try to book an apoitment tomorrow. The problem is, there is usually a month of waiting time where i live, because we only have 1 benz workshop here. Hopefully they will let me drop by to check it quickly.
 
Half a litre too much oil isn't great, obviously, and yes too much oil isn't good, and yes you should syphon some out - but too much oil in a petrol engine isn't as a big a problem as it is in Diesel engines.

I suggest that you drive the car normally and arrange to get some oil syphoned out at the earliest opportunity. I wouldn't treat this as an urgent matter.

Thats comforting to hear. Obviously, I will still try to siphon out the excess oil as soon as possible. Out of curiosity, what makes it more of an issue for Diesel engines?

A part of me still hopes maybe i have done some error in my readings. Because the funny thing is, i also measured the level when the engine was cold (it wasnt used for 9 hours). In this case the dipstick would show the level right under the max indicator, as can be seen in the attached image. However, it would do so only on half of the dipstick, and on the other half it would be 5-7mm above. Im no car expert, but from my understanding, the oil level should read even higher when the oil has had 9 hours to drain into in oilpan. Can thermal expansion of the oil really raise the volume by 0,5 litres?IMG_5959.JPG
 
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Thats comforting to hear. Obviously, I will still try to siphon out the excess oil as soon as possible. Out of curiosity, what makes it more of an issue for Diesel engines?

A part of me still hopes maybe i have done some error in my readings. Because the funny thing is, i also measured the level when the engine was cold (it wasnt used for 9 hours). In this case the dipstick would show the level right under the max indicator, as can be seen in the attached image. However, it would do so only on half of the dipstick, and on the other half it would be 5-7mm above. Im no car expert, but from my understanding, the oil level should read even higher when the oil has had 9 hours to drain into in oilpan. Can thermal expansion of the oil really raise the volume by 0,5 litres?View attachment 149125
Tell me if I’m wrong but that oil/sludge looks contaminated, by water/coolant, you should return the car asap, and don’t drive it. Head gasket failure?
 
Tell me if I’m wrong but that oil/sludge looks contaminated, by water/coolant, you should return the car asap, and don’t drive it. Head gasket failure?
What makes you think that? The car has only done a total of 34.000km, and only 2.000km since last oil change. Thats probably why the oil is so clear, if thats what raises your concern.
 
What makes you think that? The car has only done a total of 34.000km, and only 2.000km since last oil change. Thats probably why the oil is so clear, if thats what raises your concern.

yes dear, end of thread….
 
Does the oil smell of petrol by any chance ?
Yes, it does have a slight petrol odor.

I just came back from the Mercedes workshop. They tapped some oil and now it reads 3/4 in the measuring area.

I was told the overfill wasnt critical at all, and that i shouldt worry about it. And was also told that its normal for these models that a little fuel gets into the oil. They said it depends a lot on the driving style. If you do a lot of short trips and dont let the engine warm up, with lot of cold start, this could lead to petrol getting in the oil. This is the case for hybrid cars, since the engine will couple in for 30 secs from cold, then turn off again for 5-10min, then turn on again for 30-60sec, and so on.

I will monitor the oil level going forward. If it increases noticeably, I will have it checked. The car is still under warranty.
 
Hi , on my C207 with the M276 engine in it I only have a dip stick.

I travel appropriately 7000 km per year and the engine oil is so clean I have trouble reading the engine oil level.

I would have the engine oil changed to make sre all OK
 
I was told the overfill wasnt critical at all, and that i shouldt worry about it. And was also told that its normal for these models that a little fuel gets into the oil. They said it depends a lot on the driving style. If you do a lot of short trips and dont let the engine warm up, with lot of cold start, this could lead to petrol getting in the oil. This is the case for hybrid cars, since the engine will couple in for 30 secs from cold, then turn off again for 5-10min, then turn on again for 30-60sec, and so on.

Fuel dilution of the oil is more of a concern than the level being a little high as it reduces the oils viscosity and therefore it's ability to protect the engine. Interesting that MB admit that it's a problem with hybrid engines. It's not an uncommon issue throughout the automotive industry because of the introduction of direct injection engines. Hybrid operation just makes the situation worse. You may have less oil in there now but it's diluted oil. I would change the oil and make sure the car get some decent long runs to get the engine up to temperature.
 
Don't want to hijack the thread but on the 2017 w205 diesel I have recently bought the oil looks a little dark on the dipstick. It's not thick or sticky but just dark in colour. Is this reason to be concerned?
 
Thats comforting to hear. Obviously, I will still try to siphon out the excess oil as soon as possible. Out of curiosity, what makes it more of an issue for Diesel engines?

A part of me still hopes maybe i have done some error in my readings. Because the funny thing is, i also measured the level when the engine was cold (it wasnt used for 9 hours). In this case the dipstick would show the level right under the max indicator, as can be seen in the attached image. However, it would do so only on half of the dipstick, and on the other half it would be 5-7mm above. Im no car expert, but from my understanding, the oil level should read even higher when the oil has had 9 hours to drain into in oilpan. Can thermal expansion of the oil really raise the volume by 0,5 litres?View attachment 149125

The additional amount of oil that drains into the sump overnight is miniscule.

The bulk of the oil would have already drained into the sump in the 5 minutes wait after switching-off the engine just before checking the oil level.

The reason that the oil level is lower when the engine is cold is that oil expands when it's hot

For this reason the oil level should be checked when the engine is hot, and then not exceed the Max mark.

The issue is that often cars are serviced when the engines are cold, and mechanics just pour in oil up to max level. The oil than expands when hot and you have an overfill situation.

As a rule of thumb, if filling up the engine when it isn't fully hot, you should only feel up to half-way between the Min and Max, and if the engine is stone cold, then fill up to the Min mark. Ideally you should then run the engine up to normal operating temperature and re-check (and also check for leaks from the oil filter housing and from the sump plug if disturbed), but garages rarely do that.
 
Yes, it does have a slight petrol odor.

I just came back from the Mercedes workshop. They tapped some oil and now it reads 3/4 in the measuring area.

I was told the overfill wasnt critical at all, and that i shouldt worry about it. And was also told that its normal for these models that a little fuel gets into the oil. They said it depends a lot on the driving style. If you do a lot of short trips and dont let the engine warm up, with lot of cold start, this could lead to petrol getting in the oil. This is the case for hybrid cars, since the engine will couple in for 30 secs from cold, then turn off again for 5-10min, then turn on again for 30-60sec, and so on.

I will monitor the oil level going forward. If it increases noticeably, I will have it checked. The car is still under warranty.

This sounds about right.

The petro in the oil will evaporate after a good motorway run, so it's only a concern if the car only ever does short journeys that allow the petrol to accumulate, but not evaporate.

It may be counter intuitive, but engines that only do short journeys should have the engine oil replaced more frequently than high-milers, precisely because of this oil contamination issue.
 
Don't want to hijack the thread but on the 2017 w205 diesel I have recently bought the oil looks a little dark on the dipstick. It's not thick or sticky but just dark in colour. Is this reason to be concerned?
Fresh oil put into a Diesel engine can go black within minutes of the engine being started. Not usually something to worry about . The oil (if the correct oil) is designt to work under these conitions.
 
Fresh oil put into a Diesel engine can go black within minutes of the engine being started. Not usually something to worry about . The oil (if the correct oil) is designt to work under these conitions.
Thanks Petrol Pete. That's good to know, the car is actually running beautifully so I would be surprised if it was something to be concerned about.
 
Tell me if I’m wrong but that oil/sludge looks contaminated, by water/coolant, you should return the car asap, and don’t drive it. Head gasket failure?
Modern oils have ridiculous expansion.

To check the oil properly:

1. Engine oil hot. (This maybe a 20-30 minute drive depending on ambient temps).
2. Wait 5 minutes after switch off.
3. Make sure you are level ground (petrol stations are a good place)
4. Dip it and wipe a couple of times. It should be 3/4 to 1/1.
 
The issue is that often cars are serviced when the engines are cold, and mechanics just pour in oil up to max level. The oil than expands when hot and you have an overfill situation.

You pretty much confirmed my suspicion, thanks :)
 

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