Diesel exhaust fluid

Diesel Exhaust Fluid (DEF) is an emissions control liquid required by modern diesel engines. It is injected into the exhaust stream. In January 2010, the U.S. Environmental Protection Agency (EPA) brought in new emissions standards requiring medium and heavy-duty vehicles to significantly reduce engine emissions, particularly NOx and particulate matter (PM). Vehicle manufacturers use SCR to meet these standards. DEF is sprayed into the exhaust, breaking down NOx gases into nitrogen and water using an advanced catalyst system. As a result most new diesel trucks, pickups, SUVs, and vans are now fitted with SCR technology and have a DEF tank that must be regularly refilled.



What is Diesel Exhaust Fluid (DEF)?

Diesel Exhaust Fluid (DEF) is a non-hazardous solution, which is 32.5% urea and 67.5% de-ionized water. DEF is sprayed into the exhaust stream of diesel vehicles to break down dangerous NOx emissions into harmless nitrogen and water. This system is called Selective Catalytic Reduction and can be found on 2010 and later model year trucks and many diesel pickups and SUVs. DEF is not a fuel additive and never comes into contact with diesel. It is stored in a separate tank, typically with a blue filler cap.

How much DEF will my truck use?

Diesel Exhaust Fluid consumption is measured as a ratio of diesel fuel use, normally termed the "dosing rate" or "treat rate". Medium- and heavy-duty vehicles have a dosing rate of 2-3%. This means that if your truck has a fuel efficiency of six miles per gallon and a dosing rate of 3% it will use approximately 1 gallon of DEF every 200 miles.

What will happen if my truck runs out of Diesel Exhaust Fluid (DEF)?

If your truck runs out of DEF the engine's power is reduced and a solid red warning will be displayed. The vehicle’s speed will be limited to 5 mph until the DEF tank is refilled.

Where can I buy Diesel Exhaust Fluid (DEF)?

You can purchase DEF right from E.H. Wolf & Sons! Give us a call at (800)236-9653.


To learn more about DEF, call (800) 236-9653 or click here.