Several of the new-issue (2011) diesel vehicles I've driven such as the Benz E-Class and Chevy Duramax 1500 have urea tanks as part of their emissions control systems. The urea is sprayed into the hot exhaust stream ahead of the converter to spur a chemical reaction that lowers NOx emissions - if I understand it right.

Anyway, the car companies are being very coy about the cost of topping the tanks off, how often they'll need topping off - and so on. I'm wondering whether anyone has more specific information or knows where to find it?

If I were in the market for a diesel vehicle, having to deal with urea would be a big turnoff. I think I'd rather buy an older/used model instead.

How about you?