Posted By RichC on October 20, 2008
Although I’m a big fan of the new ‘clean diesels’ being produced by several companies, I’ve never like the idea that in order to meet emission standards that ‘some’ diesels require an AdBlue urea system. Basically the $4/gallon liquid is stored in a small tank and is slowly injected into the exhaust stream where it forms ammonia. This ammonia reacts with the NOx in diesel exhaust and converts it to water and nitrogen.
Volkswagen, in keeping their vehicles small, have been able to keep exhaust emissions low enough to be the only diesel vehicle currently sold in the U.S. that does not require AdBlue and the additional injection system. Mercedes, the other major ‘clean diesel’ vehicle producer for the U.S. market, uses the urea based system and the extra tank, injection system and associated idiot light/no-start system. It’s not all that difficult to maintain since the 7 gallon tank can go about 15,000 miles without replenishment; most owners can easily top off their AdBlue tanks when making oil changes or taking their vehicles in for service. But, AutoblogGreen did point out thought that “if you don’t fill that tank” that you could be left stranded. Mercedes diesel vehicles have 20 re-start limit if you permit your tank to run “critically low.” After that, you’ll need to add a minimum of 2 gallons in order to restart your car. Hmm … why not just a ‘creep home mode’ rather than putting owners in a ‘no-start’ situation?