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Urea is the first significant consumable non-fuel fluid to be added to any car or truck in the history of the automotive industry. Some people prefer to use the term “Diesel Exhaust Fluid” (DEF) instead of “urea” due to its close association to malodorous bodily fluid. Urea is a colorless, odorless substance that is used to meet the Environmental Protection Agency’s (EPA) vehicle exhaust regulations that will go into effect in January 2010. DEF in New Diesel Vehicles.
Vehicle and engine manufacturers have developed Selective Catalytic Reduction (SCR) technology, which uses DEF to convert noxious NOx into harmless nitrogen gas. While some vehicle manufacturers have committed to using the SCR technology, others will use Exhaust Gas Recirculation (EGR) technology. In EGR, a portion of the vehicle exhaust gas is recycled to the engine, minimizing the generation of NOx in the engine itself, allowing the vehicle to meet the Tier 2 standards. SCR technology has up to a five percent fuel economy advantage over EGR. The use of EGR also requires additional space for the recirculating pipes, potentially decreasing the available payload capacity. Industry projections on SCR acceptance vary, indicating that between 50 percent and 75 percent of all diesel vehicles will use SCR technology.
