In the Trucking Industry, the urea deal was originally a big issue for both the manufacturers and users. Now that urea, also known as Diesel Exhaust Fluid ( DEF ), is commonly available at truckstops and retailers ( including Walmart ) nationwide, the issue has toned down quite a bit. Where I work, the local fuel jobber now has DEF on his fueling trucks as well. Truck manufacturer Navistar ( International ) tried building their own emissions - compliant diesel engine using an EGR system, but they were never able to get it to run clean enough for the EPA standards. Now they buy their DEF - equipped engines from Cummins. Peterbilt and Kenworth were way ahead of the game on emissions controls due to parent company PACCAR's experiences with manufacturer DAF in Europe, where emissions controls have been required since the early 2000's. Caterpillar, once the # 2 builder, chose to leave the Over - the Road diesel engine market rather than mess around with the emissions deal.
My own experiences with DEF show that more fluid is used in local city driving than Over - the Road. I have heard of only a few issues and breakdowns with the emissions controls, most involving the computers and sensors rather than the actual cleaning agents themselves. The biggest issue so far seems to be decreased fuel economy, and the room required on the frame for the emissions box and DEF tank. Of course this also means increased tractor weight in an industry that has been driving manufacturers to bring down dead weight and increase fuel economy. The emissions box also generates A LOT of heat, and takes up room on the frame that could be used for larger fuel tanks. Since the diesel truck emissions issue is so new, it will be interesting to see what costs are involved with replacing the scrubber when it reaches the end if its' useable lifespan of around 350,000 - 400,000 miles.