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Mercedes AdBlue fluid for Diesel models

Many Mercedes-Benz diesel cars such as E220, C220, S350, G350, ML350, ML250 equipped with BlueTec technology use AdBlue® Diesel Exhaust Fluid (DEF). The AdBlue fluid is sprayed in the exhaust gasses and lowers the NOx emissions.

If you see an AdBlue Warning light on your instrument cluster, it may be time to refill your Mercedes-Benz with AdBlue. Typical AdBlue messages are:

  • Refill AdBlue at Workshop
  • AdBlue Check Additive See Operator’s Manual
  • AdBlue Range
  • Engine Start Not Permitted (AdBlue Empty)
  • Check AdBlue No engine Start Possible in XXX miles/km.
  • Refill AdBlue See Owner’s, Manual
  • AdBlue Should be refilled at the next opportunity

It is important to realize that if the AdBlue level reaches zero, you will not be able to start your car. In such cases, you will get a warning message that says “No engine start possible.constantly”

Where to buy Adblue for Mercedes-Benz?

AdBlue used in Mercedes-Benz cars is developed by a European company called VDA ( Verband der Automilindustrie). If you are looking to buy AdBlue for Mercedes you have several options. You could either buy AdBlue fluid from Mercedes-Benz dealership and add it yourself. A very popular Mercedes AdBlue alternative that many owners use is the BlueDEF Diesel Exhaust Fluid

Buy AdBlue for Mercedes

How long does AdBlue last?

Typically  5  gallons of AdBlue will last anywhere from 10k-15k miles. The range will vary depending on driving habits.

How to add AdBlue to a Diesel Mercedes

Adding AdBlue to Mercedes-Benz BlueTec cars such as W221, W463, W166 is very easy and simple.

  1. Open the fuel door lid.
  2. Note the blue cap next to the fuel fill cap.
  3. Add the required AdBlue. Don’t mix AdBlue with diesel fluid.

Make sure to add AdBlue to the correct tank. Do not mix AdBlue with diesel fluid. AdBlue is not an additive or a lubricant. Do not mix water with AdBlue.

Mercedes AdBlue Capacity

Typical capacity for Mercedes-Benz AdBlue tank has a 5 gallon capacity. . You don’t need to add AdBlue every time you get gass.

Recommended AdBlue service:

• Every 10k miles refill with AdBlue

• Every 20k miles drain tank and refill

Make sure to add AdBlue as soon as possible if you get a message on your instrument cluster that the AdBlue level is low.

If the warning light comes on asking you to add AdBlue, you need to add diesel emissions fluid. Otherwise, your engine won’t start when the AdBlue level reaches 0. Typically you have about 1000 miles from the point that you see AdBlue warning light until the system reaches zero. Don’t get stranded or stuck in a parking lot. Add AdBlue. AdBlue is cheap and easy to add.

Mercedes Adblue Reset

In most cases, the AdBlue warning message should turn off after a few driving cycles. If it doesn’t try turning the key to position one (1st click, accessories on) and wait for at least 30 seconds. Next turn off the ignition and wait a few seconds.

Instructions for AdBlue adaptation. 

  1. Turn ignition on once
  2. Press and hold the gas pedal. Keep the gas pedal pressed until the glow plug comes back on. Once the glow plug turns back on, remove your foot from the gas pedal. The glow plug light should flash a few times.
  3. Wait for the glow plug light to stop blinking. Then turn off the ignition.
  4. Wait 10 seconds with the ignition off.
  5. Turn the ignition back on.
  6. Press the gas pedal two times. The second time you press the gas pedal continues to hold it pressed until you see the glow plug to turn back on. Next release the

If you would like to learn how to erase fault codes from the SCR system with Star Diagnostic watch this video. 


Mercedes Adblue Delete / Bypass

mercedes adblue bypass module emulatorYou may have heard about Adblue bypass module.  Installing AdBlue bypass module may be in violation of laws in your Country or State. It is important to understand the legal requirements and the impact that you will have in the environment. AdBlue bypass module will emulate a full AdBlue tank. Your Mercedes-Benz will run fine, but it will pollute more since there will be no AdBlue fluid injected into the exhaust gasses to reduce the harmful Nox gasses.

These modules bypass the AdBlue system and don’t use any AdBlue fluid. The module is installed in the trunk and requires that you make connections to existing wire harness.

Mercedes AdBlue Heater

Mercedes AdBlue HeaterOne of the failure points of the Mercedes AdBlue system is the AdBlue heater or the processor. If your Mercedes-Benz is still under warranty, you should have the dealer fix this problem free of charge. If you are out of warranty, consider replacing the AdBlue heater yourself with a replacement unit if you are looking to minimize repair cost.

Check prices on Mercedes AdBlue heater (eBay link).

Mercedes BlueTec AdBlue SCR NOx Diagnostic

It is possible that the AdBlue system on a Mercedes-Benz fails. If you are trying to diagnose a problem with the AdBlue / SCR system watch the following video.

AdBlue Fault Codes

Below is a list of typical fault codes you may see on your Star Diagnostic Scanner.

  • Engine AStart is not possible
  • The upper limit value for long term adaptation of SCR exhaust after treatment system was exceeded
  • Starting the engine is not possible due to malfunction in the AdBlue system
  • The remaining driving distance is limited due to a malfunction in the AdBlue system.

Additional Resources:



  1. I used the Walmart BlueDEF with the ISO 22241-1. Not long after that, check engine warning light came up.. The dealership had to replace the AdBlue heater. The MB service advisor recommends only to buy their AdBlue. My question is the AdBlue’s equivalent DEF manufactured by the company in the US, bluesky.

    • Use whichever DEF that you feel comfortable with. I think it was a coincidence that your AdBlue heater failed at the same time you switched brand. Many owners use other brands of DEF instead of AdBlue without any problem.

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