Clearing the Air - w/ a Diesel and UREA.

WHY UREA? Selective catalytic reduction, which uses urea to scrub NOx from diesel exhaust, offers these advantages. Simplicity: Automakers can meet the toughest emissions standards on the books with a system that could be used in all markets. Cost: Depending on the vehicle, a urea system could cost about half as much as the alternative, a lean NOx trap. Integration: The system does not affect engine performance and could be installed without extensive modifications to the vehicle or engine.