What is the function of the DEF system in diesel trucks?

The function of the Diesel Exhaust Fluid (DEF) system in diesel trucks is primarily to reduce nitrogen oxide emissions. The DEF is a non-toxic, clear solution made from urea and deionized water that is injected into the exhaust stream. When the DEF is introduced to the hot exhaust gases, it undergoes a chemical reaction that converts nitrogen oxide (NOx) emissions into harmless nitrogen and water vapor. This process is known as Selective Catalytic Reduction (SCR).

By using the DEF system, diesel engines can meet stringent emissions regulations while still delivering the performance required for heavy-duty driving. The system is an important component in helping reduce the environmental impact of diesel engines, ensuring compliance with modern emission standards.