Diesel Exhaust Fluid

Starting in 2010 diesel engines have to meet stringent emission requirements. Most diesel engine manufacturers have chosen a technology called Selective Catalytic Reduction (SCR) to meet these requirements. If you operate a vehicle or equipment that utilizes SCR technology, you need DEF.

Diesel Exhaust Fluid (DEF) is a very pure solution of urea which meets the automotive industry specification defined by ISO 22241. It is a clear liquid similar in appearance to water. DEF is safe to handle and use. It is not explosive, flammable, toxic or subject to any hazardous product regulations. When properly stored it a shelf life of 24 months.

Since you will use less DEF than diesel, the DEF tank will be smaller than the diesel tank. It will be clearly marked as DEF and is likely to be mounted next to or near your vehicle diesel tank. It is important that you do not put diesel in the DEF tank or DEF in your diesel tank. Some vehicles will have safeguards to ensure this doesn't happen but this might not be the case on all vehicles - so make sure to check!

Your vehicle will also be fitted with a DEF gauge near your fuel gauge so you will know when you need to fill up with the fluid. If you run out of DEF, your catalytic converter could be damaged which may void your vehicle's engine warranty.

Douglass Distributing can also handle all your DEF packaging needs.

Tips on how to use DEF


  • Only fill DEF into the tank. Both nozzle and outlet are clearly marked.
  • Keep your DEF equipment clean and free from dust or dirt.
  • You do not need to wear protective clothing while filling DEF.
  • If overheated, DEF containers can be chilled by standing in water.
  • DEF freezes at 12 F
  • Only use DEF that has been delivered in dedicated, sealed DEF packages.


  • Do not fill DEF into the Diesel tank!
  • Do not fill Diesel into the DEF tank!
  • Don’t get DEF on you clothes and skin. If you get DEF on your skin, flush the area with cool water, then wash with soap and water. If you get DEF on your clothing, wash the contaminated clothing in a separate load.
  • Don’t get DEF in your eyes. If you do, flush your eyes with cool water.
  • Don’t allow DEF to remain on surfaces as it can damage concrete or masonry, and create a slipping hazard. If spilled, wash the surface with water.
  • Do not use DEF when mixed with water or other substances, especially diesel fuel.
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