SCR and EPA 2010
Beginning with diesel engines manufactured on or after January 1, 2010, the engines are required to meet lowered NOx standards for the US market.
All of the heavy-duty engine (Class 7-8 trucks) manufacturers except for Navistar International and Caterpillar Inc. continuing to manufacture engines after this date have chosen to use SCR. This Includes Detroit Diesel (DD13, DD15, and DD16 models), Cummins (ISX, ISL9, ISB6.7, and ISC8.3 line), PACCAR, and Volvo/Mack. These engines require the periodical addition of Diesel Exhaust Fluid (DEF, a urea solution) to enable the process. DEF is available in a bottle from most truck stops, and some have put in bulk DEF dispensers near the Diesel Fuel pumps. Caterpillar and Navistar had initially chosen to use Enhanced Exhaust gas recirculation (EEGR) to comply with the Environmental Protection Agency (EPA) standards, but in July 2012 Navistar announced it would be pursuing SCR technology for its engines, except on the MaxxForce 15 which was to be discontinued.
A stock 2012 VW Passat TDI equipped with an SCR that fulfills emissions requirements in all 50 states set the world record for longest distance on one tank of clean diesel fuel May 11, 2012.
Read more about this topic: Selective Catalytic Reduction