Fleetowner top story: Paccar officially rolls out MX engine for Kenworth and Peterbil

EGR: Exhaust gas recirculation. Exhaust is a so-called "neutral" gas because it contains no oxygen in it. It is used to lower the NOx (when mixed with water in the air turns to nitric acid...which is what makes acid rain just that) output of the engine. Increasing EGR, increased the amount of partially burned diesel out of the exhaust (particulate or black smoke)

DPF: Diesel Particulate Filter. This is used to trap the particulate created by a diesel engine. Just like the catalytic converter in a gasoline engine the DPF has a catalyst inside to convert unburned fuel CO2. Of course diesel particulate isn't as easy to convert as unburned gasoline is so sometimes they have to help out the filter by injecting regular diesel into the filter and essentially burning off what has been trapped (a regeneration cycle)

SCR: Selective Catalytic Reduction. This is used to convert NOx in the exhaust stream to N2 and water. It does this by having, you guested it, a catalyst (iron zeolite, or copper zeolite) and injecting Urea (pee) into the exhaust. Europe has been using this for quite some time.

 

There was some idea to make it out of cow pee from feedlots... but they couldn't figure out how to make the purity high enough without other problems. So now they just make it out of ammonia and CO2.

DEF (diesel exhaust fluid) is 32.5% urea versus regular pee which is something like 2% but I have been waiting to hear about somebody that buys a truck and plumbs a hose from the cab to the tank...