To meet North American exhaust emissions laws on the new diesels introduced this year, BMW has moved to Selective Catalytic Reduction (SCR) to reduce NOx. This system is known as Bluetec, or Adblue, or by other names depending on the manufacturer.

The system injects urea (made from uric acid, commonly cow urine) into the exhaust. The ammonia reacts with the NOX, and you end up with cleaner exhaust. The urea tank needs to be replenished, usually after 10,000 miles or so.

BMW diesels in other markets don't have the same emissions requirements (their regulations typically focus more on CO emissions than on NOx). So, this is a new system this year for diesels in the US and Canada. Not sure if it will be coming to Europe, but I expect so, just not sure when.

There have been reports of ammonia smell with the X5 diesel in North America. I suggested in an earlier thread (on another site) that it may be the urea tank or injection system malfunctioning. In normal operation, urea injection shouldn't cause an ammonia smell. It may just be new model introduction issues. I trust they will resolve it, but in the meantime it will be a pain (and a smell....)

Here is the other thread: http://www.bimmerfest.com/forums/sho...d.php?t=338456

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2007 X3 3.0si, 6 MT, Premium, White

Retired:
2008 535i, 6 MT, M Sport, Premium, Space Grey
2003 X5 3.0 Steptronic, Premium, Titanium Silver
2002 325xi 5 MT, Steel Grey
2004 Z4 3.0 Premium, Sport, SMG, Maldives Blue