By now, you should know what SCR and DEF stand for, but if you don't I'll recap: SCR stands for Selective Catalytic Reduction, the technology that most of the major diesel engine manufacturers have chosen to meet the EPA's 2010 diesel engine emissions standards, and DEF stands for Diesel Exhaust Fluid, the urea solution that is injected into the aftertreatment system of a truck with an SCR engine. Last week at the Mid-America Trucking Show in Louisville, KY, you could hardly go five minutes without someone talking about SCR and DEF, and the conflict that has erupted between the OE's that will be using SCR and DEF in 2010 (Daimler, PACCAR, Cummins, Volvo and Mack) and those that will be using "enhanced EGR" (Navistar/International). The...