Diesel exhaust fluid

Diesel Exhaust Fluid (DEF) is a non-hazardous product that consists of 67.5% de-ionized water and 32.5% urea. It is not a fuel additive and cannot be combined with diesel fuel, but rather is contained in a dedicated tank for diesel engines and injected into the exhaust system using a Selective Catalytic Reduction (SCR) system

The EPA is changing emissions standards for NOx emissions, particulate matter and other pollutants from diesel engines. DEF is used in the emissions systems on new diesel powered equipment to meet these standards.

When DEF is injected into the exhaust using a SCR system, it combines with a catalyst to break down NOx into nitrogen and water. In addition to reducing emissions, the added benefits of this system are increased fuel efficiency and longer oil change intervals.