Diesel Exhaust Fluid
What is 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, many diesel pickups and SUVs. DEF is not a fuel additive and never comes into contact with diesel.