Ad-Blue DEF warning for Mercedes diesel owners
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Junior Member
Joined: Sep 2013
Posts: 57
Likes: 6
GL 350
Ad-Blue DEF warning for Mercedes diesel owners
A general warning for any user of a diesel vehicle that uses Ad-Blue (diesel exhaust fluid or DEF)
I just read an article on serious problems caused by people putting Ad-Blue DEF in the diesel tank. Apparently, the Ad-Blue DEF can cause terrible corrosion problems in the fuel system, and the only cure is the replacement of the whole fuel system, which is very expensive. If Ad-Blue DEF is accidentally put in the diesel tank, (any quantity, even a ½ teaspoon is bad news) you should do the following.
1. If the engine is not off, immediately shut down the engine and if possible, disconnect the battery to prevent accidental starting.
2. Call a tow truck and have the vehicle taken to the nearest facility that can flush out the fuel system.
3. Drop the tank, dispose of the contaminated fuel, and flush out the tank thoroughly.
4. To be safe, flush out the fuel line to the filter and replace the fuel filter.
This should be done as soon as possible, because the Ad-Blue DEF will start corroding the fuel tank very quickly.
I just read an article on serious problems caused by people putting Ad-Blue DEF in the diesel tank. Apparently, the Ad-Blue DEF can cause terrible corrosion problems in the fuel system, and the only cure is the replacement of the whole fuel system, which is very expensive. If Ad-Blue DEF is accidentally put in the diesel tank, (any quantity, even a ½ teaspoon is bad news) you should do the following.
1. If the engine is not off, immediately shut down the engine and if possible, disconnect the battery to prevent accidental starting.
2. Call a tow truck and have the vehicle taken to the nearest facility that can flush out the fuel system.
3. Drop the tank, dispose of the contaminated fuel, and flush out the tank thoroughly.
4. To be safe, flush out the fuel line to the filter and replace the fuel filter.
This should be done as soon as possible, because the Ad-Blue DEF will start corroding the fuel tank very quickly.
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From: New York
2025 Range Rover, 2022 BMW M850 , 2017 MB E400 Coupe
Hmmm...are there actual people who've done it ? I can't think of any scenario when I could switch these 2 holes, unless I'm dead drunk...
Thread Starter
Junior Member
Joined: Sep 2013
Posts: 57
Likes: 6
GL 350
Yes. Apparently there are a variety of mistakes. Some uneducated or ignorant person servicing the vehicle, careless mistakes, guys using DEF fill nozzles accidentally at truckstops etc. From my experience, if it is possible to make this type of mistake, somebody will do it. And, apparently some people feel it is fuel additive, such as a anti gelling compound. Earlier in this forum we heard about people filling MB diesels with gas and killing the injectors.
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From: Toronto
2005 ML350, 2008 GL320, 2013 Gl350
I would not be surprised if an MB service centre accidentally did this as well. It has probably already happened, i.e the 16 year old intern students they hire to do mediocre work for free around the shop
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From: San Diego
MB GLS550/BMW 550/2017 Acura NSX
