DEF in the DEF Tank, YES; DEF in the Diesel Tank, NO.

Diesel Exhaust Fluid (DEF) is a vital component of a Select Catalytic Reduction (SCR) system. It’s a clear solution made of Urea and water that’s colorless but has the smell of ammonia. When added to the system, it enters the exhaust stream, where it breaks down Nitrogen Oxide emissions into Nitrogen gas and water vapor – two basic components of the air we breathe. Your machine has a separate DEF tank that varies in size depending on what model you’re running, and it usually has a blue cap for easy identification.

 The DEF tank is for DEF, not diesel. The diesel tank is for diesel, not DEF.

If you put diesel into a DEF tank, diesel is less dense than DEF so that it will float on the DEF. If diesel enters the SCR catalyst, significant damage can occur that may require servicing or a costly replacement of the catalyst. If you put DEF into a diesel tank, the diesel becomes contaminated because DEF is composed of urea and water. If the equipment is started, introducing the diesel/DEF mixture into the engine, you’ll end up with longer term consequences. If the DEF is introduced to a diesel storage tank, the DEF will, if not removed, cause damage to the fuel system. DEF is corrosive and harmful to many metals.

2 thoughts on “DEF in the DEF Tank, YES; DEF in the Diesel Tank, NO.

  1. I left some def in the original container in the back of my sprinter c70 all summer. I put it into the def reservoir yesterday and immediately the check engine light came on and the low def message would not go off. What do I do? I know not that exposure to high heat will make def go bad.

    • DEF shelf life depends on the temperature of your storage facility. It is recommended that DEF be stored between 12°F and 86°F, but when stored below 65°F, shelf life is extended to 2 years. It is recommended to store DEF in a climate-controlled environment and out of direct sunlight to extend shelf life.
      It sounds like you will need to take a trip to the Sprinter dealership so that they can test the emission system and see what damage was done and have it repaired properly and reset the emissions system afterwards.

      We would highly recommend that you purchase a inexpensive def tester and test your DEF fluid before you pour it into your equipment, it can save you a lot of time and money, and prevent a unexpected break down, we hope it works out for you.

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