It looks like Mercedes won't be the only car-maker using urea injection to help their diesel engines meet tough new US emissions standards. The problem that all car-makers have with diesels is nitrogen oxide emissions. In order to minimize unburned hydro-carbons and fuel consumption all engines (gas and diesel) have been moving toward leaner fuel-air mixtures and one side-effect of this is extra nitrogen oxide production. One way to get around that is to expose the exhaust to ammonia. This causes the nitrogen oxides to convert to water vapor and nitrogen gas. Injecting an aqueous urea solution known as AdBlue, provides the necessary ammonia. This system was developed by Mercedes-Benz and Bosch and commercialized under the name BlueTec. Mercedes already announced their intentions to sell a 50 state legal BlueTec system in 2008. Now they have reached an agreement with Volkswagen group to use BlueTec on VW and Audi diesels and are close to finalizing a deal with BMW as well. It's great that DaimlerChrylser has chosen to share this technology, because diesels are an important step to reducing fuel consumption and in turn greenhouse gases. The only problem with the BlueTec solution is the need to replenish the urea supply periodically. The three car makers are all planning to show BlueTec equipped diesel vehicles at the Los Angeles Auto Show in December. VW will be showing their new Tiguan compact SUV, and Audi Q7, BMW will have the diesel version of the new X5, and Mercedes will have the R, ML and GL class diesels.