Reduce Oil Level in Mercedes – What's Wrong?

A modern Mercedes vehicle has a lot of sensors that do the job for you. Earlier, you had to check the oil manually using the dipstick. In a modern car, you will not find a dipstick, the oil level is checked by the sensors and you can check it by sitting in your leather seat and tapping on the screen of the infotainment system. Who thinks it's an improvement? I don't.

Reduce oil level message highlights

• Common reasons:high oil level, head gasket broken, fuel in oil
• How to fix:check the oil level, don't drive if you can't do this
• Possible consequences:engine may fail
• Priority level:High
• Can you drive?Not recommended
• DIY repair:Impossible
• Repair price range:$200-$900

What should you do when you see this message?

Many of us may think that a high oil level means nothing bad. Everyone knows that any car owner should avoid low oil levels in the engine. But a high level means the engine should be lubricated properly and everything should be fine. But no. Remember those good times when we had a dipstick in our engines? On the dipstick, you could see two lines - MIN and MAX. So, the MAX line was as important as the MIN one.

Ignoring high oil levels in your vehicle is a bad idea. Here's what may happen because of this:

• catalytic converter death;
• oil getting into combustion chambers and burning;
• soot and buildup in the engine;
• tough work of the crankshaft that is floating in oil;
• high load on the engine and poor efficiency.

Actually, a modern engine can seize if it has a really high engine oil level. What's more, the reasons for the high level of oil are uncertain and this is not a natural condition of your engine. If this happens, there may be a serious problem with some important parts of your vehicle.

Here's what I recommend doing, in this case:

• stop the car once it's safe and turn off the engine;
• if you have the dipstick, check the engine oil level;
• also, pay attention to the color and condition of the oil;
• if you notice any anomalies, just avoid starting the engine again and call for help;
• if you don't have the dipstick in the engine, use an electronic way to check the engine oil;
• if the system malfunctions, it's most likely the sensor fault and you can keep driving;
• if the level is actually high, you will need to check several other things;
• open the hood and see if the coolant reservoir is OK - no oil stains, the coolant is of good bright color;
• open the oil cap and smell the engine - it shouldn't have a very distinctive gas smell.

So, these are pretty simple things you can do to find out whether it's OK to drive further. If you notice some really bad things like oil film inside the coolant reservoir, black coolant color, no coolant in the reservoir, white oil, or bad gas smell from the engine, you should definitely avoid driving.

In these cases, the oil in your engine may be mixed with a lot of coolant or gas and it can lubricate the engine poorly. This means that if you keep driving your vehicle this way, you will most likely kill the much faster than you think.

What are the common reasons for high oil levels in Mercedes cars?

If your Mercedes starts showing the "Reduce Oil Level" message on the screen, it means that its sensors registered some anomaly with the oil level and now the sensors are sending the signal to the ECU, a certain error code forms there and you see the message. This will not affect the way you can drive your car, but please follow the recommendations given above to avoid issues.

So, here are the reasons why you can see this message:

1) Mechanics overfilled your engine with oil

This is a more common problem than you think. Mechanics may overfill the engine if they check the level with the dipstick or with the sensor system. Once they pour the needed amount of oil and go to check it, they will find the low level because not all oil is down in the pan. Any oil is pretty viscose and needs some time to get down to the oil pan.

Many mechanics will not think about that and will pour some more oil to make sure it's on a normal level.

Also, it's not uncommon for mechanics to mistakenly look at the specs of another engine and pour more oil than needed in your engine. Anyway, this is the first thing to check if you get the message within the week or two after the oil change.

2) The oil level sensor is broken

Fortunately, it's not the most expensive part of your vehicle with the retail price at about $90. The sensor is pretty reliable and it's not common to fail, but such things may happen. Checking the oil level sensors is not that easy, so you may just need to replace them if there is no other reason for this problem.

3) Antifreeze is pouring into the engine

There are several ways the antifreeze can get into the engine and mix with oil. There are several heat exchangers where oil is cooled. They may leak and eventually, the coolant gets into the lubrication system or vice versa.

If your engine oil is mixed with coolant, it becomes white in color, loses its properties, and forms a lot of foam. But you won't notice it unless you actually see the oil. So, it's important to check the coolant level and make sure it doesn't leave the system.

Common problems that lead to this issue are block cracks, turbocharger failures, or heat exchanger cracks.

4) Gas is poured into the cylinders

In old and worn-out engines, gas may get to the cylinders after not being burned for some reason. The loose piston rings just let it flow down the cylinders and dilute oil. This not only raises the level of oil in your engine but also changes its properties. Basically, your engine will not get lubricated at all.

Diluted oil is thin and loses its viscosity. It will also lead to an eventual drop in oil pressure. If the problem is ignored, the engine will basically come to an end very soon.

This usually happens because of broken or clogged injectors, ignition issues, bad piston rings, etc.

5) You added oil when it wasn't needed

You may have seen the "Add engine oil" message and obeyed this command by your Mercedes car. However, the problem is that the oil level sensor system relies on several sensors. One of them checks the minimal oil level, the other registers pressure, and the third one checks the maximum level. If the one that measures the minimum level of oil fails, it may eventually lead to an "Add engine oil" message even if the engine oil is OK.

Any DIY fixes?

You can try to suck out some engine oil using a simple syringe, or a silicone tube (basically, I've used the system for medical dropper). But if you don't have the dipstick, you can't insert this tube into any certain place. What should you do?

Well, almost all engines still have the dipstick but it's hidden. Or they may have the dipstick tube covered with a cap. Try locating one of those.

Also, you can do this by unscrewing your oil filter if it's located in the top part of the engine. Using the oil filter tube for this may even be more convenient.

Note: you should try this in that case only if you are really sure the problem is just with overfilled oil! This method won't solve all your problems if the oil is diluted by gas or mixed with coolant.

Suck out the oil by 0.3 quarts and check the level using the electronic system. Once it's OK, start the engine and see if the "Reduce Oil Level" message is gone in your Mercedes. The optimal level for the majority of MB engines is about 2/3 of the maximum level.

When will you need professional help?

You can try several DIY fixes if the problem is caused by the high engine oil level. Also, some Mercedes owners can replace the oil level sensor on their own. But this is it. If you notice that the problem is because of some issues with gas dilution or internal coolant leaking, you need professional help.

It's important to not ignore the problem. Even one hour of driving in this condition can lead to unpredictable consequences.

Don't drive your car to the dealership if you suspect a serious problem. You better pay $150 for a tow truck than $10K for engine replacement.

Final thoughts

Although the "Reduce Oil Level" message is almost always shown in Mercedes cars because of problems with overfilled engine oil or sensor glitches, it's worth making sure the engine hasn't developed one of the fatal problems. It's not that hard to check if you follow the recommendations given above in this article.

I strongly recommend asking for professional help if you can't locate the issue. Ignoring the problem and driving your car like this can lead to severe consequences for your engine.