Not sure where to post this, but just came across some info on where to buy "AdBlue" for newer SCR diesels. MB want's $11-$14/half gallon bottle, VW only wants about $15 for 2.5 gallons.
That's a very reasonable price from VW. I would guess that the Mercedes would use the exact same 32.5% urea solution.
The Touareg holds about 4.5 gallons of solution and that'll last the average driver nearly a year. I'd probably spend more money on windshield washer solution than I would AdBlue.
This whole diesel treatment chemistry is very fascinating to me. My Jetta doesn't require a additive but I wonder if possibly 10 years from now will I receive a anonymous package from UPS containing 10 years worth of diesel soot that has been mysteriously stored for me someplace in area 51, Nevada.
I think VW, MB and BMW all are the 32.5% UREA solution. It seems like that's the industry standard, thankfully.
Pilot Travel Centers are starting to install AdBlue pumps for the newest big-rigs which have SCR systems. I haven't seen pricing yet though. Looks like they will also sell individual bottles too! My guess is that will be cheaper than any dealer would ever be. http://www.findadblue.com/newsarticle101489.aspx
I've been looking a lot online on urea/AdBlue and from what I've read it's perfectly fine to use after it's thawed. Apparently the Urea has a shelf life though of a year or two, then it's "bad".
It seems that the MB and BMW diesels (at least) with the system have a holding tank heater. The car runs without injecting the AdBlue intially (since it's frozen) then it will squirt as it begins to melt.