What happens if you put Diesel Exhaust Fluid in your diesel tank?


DEF equipment Houston TexasWhat happens if I pour Diesel Exhaust Fluid inside my diesel tank? This is by far the no.1 question online; throughout all multi media channels.

We have been researching this question for sometime but need your help in filling in the blanks, the point of this entry is to help those of you searching for answers like this.  

So, first of all; Diesel Exhaust Fluid has the traditional blue cap on the tank.  Diesel also has a colored coded cap and it is typically green.  With that being said, we are unclear as to where the problem may be happening; at the retail pumps or private locations?  If you have some input, let us know here so that we can update this entry.

Ok, let’s jump in. Keep this in mind, the dispensing nozzle for Diesel Exhaust Fluid is smaller than the diesel dispensing nozzle.  So, what may be happening is that the DEF dispensing nozzle is finding its way into the diesel tank.  Of course, you cannot take the diesel nozzle and put it inside the DEF tank because of the larger diameter.  Keep this in mind. 

We found ourselves in different forums adding to this ongoing conversation and here is what we have found thus far.   The main problem lies with the corrosiveness of DEF.  So if we assume that there is a misfill of DEF into the diesel fuel tank, the problems that you will encounter may occur as DEF (although classifed as a non hazardous chemical) is corrosive to some metals. This of course leads will have a negative effect inside the compelte fuel system.  Again, keep in mind that the material’s used inside the fuel lines may not be compatible with Diesel Exhaust Fluid.


DEF houston texasWe are aware of engine failure reports, but again no hard informatio on the step by step pricess to what to do next.   The next logical place to look for data is into the AdBlue market in Europe; hoping to have a little more history and comments in those forums.  We also continue to look for OEM data to be availabe, if you know more information please post here. 

The very nature of this technology being new to the USA is what is sending people searching for answers.  So again, the biggest concern seems to be corrosiveness inside the fuel supply/engine. We do not claim to have clear answers but we will take a stab at trying to guide those that have unfortunately been hit with this dilema.

We all know that Diesel Exhaust Fluid is 67.5% water, and 32.5% Urea. Since water is the bulk of the composition on DEF; the areas of concern may be the following: (aside from the corrosivenes we have already highlighted).



1. Injectors may need to be removed / cleaned propertly.

2. All fuel lines, fuel pump, must be propertly flushed and cleaned.

3. Fuel filters must be serviced.

4. Remove the water fuel separator and install new one.

5. Remove and flush all existing fuel from the tank and inspect the tank.

6. Inspect fuel line assembly, fuel vent fittings; and hoses.

7. Address probem right away.  DEF sitting in the engine will cause much more damage due to the corrosiveneness of Diesel Exhaust Fluid (DEF).

Common sense tells me not to start the engine, and drain the tank immediately to avoid any further contamination. 


Transliquid technologiesOk ladies and gents, chime in and let’s build a good white paper to help our young industry.