[GermanStar]

Mercedes-Benz's much trumpeted E320 Bluetec diesel has failed to meet the emissions standards required for sale in green-minded California and four other states in the USA. Mercedes had hoped that Bluetec technology would establish the brand as a maker of clean, low-emissions diesels as the US market slowly turns towards higher-economy vehicles, but potential buyers in wealthy Maine, Massachusetts, New York and Vermont, as well as highly pollution-conscious California, won't be able to buy that version of the E-Class.

The Bluetec system includes injection of the AdBlue fluid, an aqueous urea solution, into the exhaust tract; this reduces nitrogen oxide emissions to hydrogen and water. In combination with an exhaust gas catalyst, a particulate filter, the latest common-rail piezo-injection technology and low-sulphur diesel fuel, the system is claimed to make the E320 CDI 'the cleanest diesel vehicle in the world', according to Mercedes. However, the testing authorities have clearly decided that it is not quite clean enough.

This decision may now delay sales of the GL 320 CDI and other upcoming DaimlerChrysler diesels, such as the Jeep Grand Cherokee, in the US. It could also delay development of the hybrid diesel-electric powertrains which Mercedes is currently working on. Sales of Bluetec diesel models in Europe are unlikely to be affected, however; the first of these will arrive by 2008.

The US Environmental Protection Agency is said to be drawing up a series of regulations for urea-injection and other such emissions-control technologies, including guidelines for owner safety and monitoring of fluid levels. This is in preparation for new diesel emissions legislation to come into force in the US in 2010, which will require diesels to meet similar emissions standards to petrol models. article continues below