What You Need To Know About Diesel Exhaust Fluid (DEF)

What You Need To Know About Diesel Exhaust Fluid (DEF)Diesel Exhaust Fluid (DEF) is used to meet the strict US EPA emissions regulations for diesel engines. DEF is a fluid that is injected into a Selective Catalytic Reduction (SCR) system. The SCR technology uses an urea based DEF and a catalytic converter to significantly reduce the emissions of nitrogen oxides (NOx). The higher oxygen levels provided by DEF results in a more efficient combustion. This equates to clean nitrogen and water emissions and maximized fuel efficiency.

It’s important to note that the United States Environmental Protection Agency (US EPA) will limit NOx levels and will require North American trucks to be equipped with SCR after 2010.

DEF is stored in a tank onboard the vehicle, and injected into the exhaust stream by a metering system at a rate of 2% of diesel consumption volume. Newer trucks have storage systems available that will hold up to 20 gallons.

Selective Catalytic Reduction and Diesel Exhaust Fluid systems are really not that intimidating once you do some research and learn what you need to know about them.


According to RelaDyne, here are some key points about DEF:

  • If DEF is kept to temperatures between 15ºF and 65ºF (-9ºC and 18ºC), it will last a minimum of 1 year
  • Big bulk dispensers (1,000 gallons) have internal climate control systems
  • In colder regions, it is recommended to store DEF in a storage unit
  • In warmer regions it is recommended to store DEF in a shaded area.
  • There are new climate control systems, designed specifically for DEF



Leave a Reply

Your email address will not be published. Required fields are marked *