Mercedes' new BlueTEC diesels will not start if urea runs out

Those of you planning to buy the new Bluetec diesel SUVs from Mercedes Benz will want to make sure you don't miss your regular service intervals or ignore warning lights. If you do, you might find yourself stranded at the mall. In order to meet new NOx emissions standards these vehicles and others from Volkswagen/Audi (not including the Jetta) and BMW use a urea injection system to eliminate almost all the NOx. The urea is stored in liquid form a tank on board the vehicle and slowly injected into the exhaust stream where it forms ammonia that reacts with the NOx and converts it to water and nitrogen. The tank is sized so that the vehicle should be able to go close to 15,000 miles without replenishment. The 7-gallon tank will be topped up at the regular 10,000 mile service interval. However, as with fuel, urea consumption is in part a function of driving conditions. If a service is missed or extra urea is consumed, a warning light and counter will appear in the gauge cluster. When the urea level gets critically low, the counter will give you 20 re-starts, after that the car will not start until at least two gallons of urea are added to the tank. Mercedes will be selling spill proof bottles of urea at dealerships that drivers can use to top up their tank, however this will automatically be part of the regular service along with oil and filter changes. Mercedes roadside assistance will also be able to top up the urea tank for stranded motorists. The urea solution, or AdBlue as it's called, will initially cost about the same as diesel fuel or about $4 a gallon, so filling at the 10,000 mile interval should cost less than $30. Check out our first drive impression of the Mercedes BlueTec diesels here.

[Source: Automotive News - Sub. req'd]

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