View Here : Diesel Exhaust Fluid
The diesel exhaust fluid solution is a component of the Selective Catalytic Reduction system now present on diesel engines. The system The Selective Catalytic Reduction systems lowers the level of nitric oxide and nitrogen dioxide, two gases that are produced during the diesel combustion process.
As of 2014, most new, large-displacement off-road diesel engines (75 horsepower and up) use DEF to meet Tier 4 Final emissions regulations. The fluid is injected into the exhaust stream and, in the presence of catalysts, turns smog-inducing NOx into harmless oxygen, water, and nitrogen. New on-highway diesel engines have been using DEF since 2010.