I researched this a few years ago after I was unable to determine from Mercedes what was special about their coolant.
Other sources indicated that Mercedes and most other European and Japanese OEMs use ethylene glycol based antifreeze without inorganic salt inhibitors such as silicates and phosphates. Rather, they use an organic corrosion inhibitor package based on carboxyate technology. I believe the the Zerex G-05 mentioned in the prior post is a so-called "hybrid" that uses a combination of both organic and inorganic technology. All current Chryler/Dodge models are using a hybrid now, but I'm not sure if current Mercedes cars are using a hybid or their tradtional organic.
About the time I looked into this GM had just come out with Dexcool - a new inorganic inhibitor blend. Though Dexcool is slightly different than the traditional Mercedes blend, it accomplishes the same end - it provides excellent protection for aluminum WITHOUT preciptating out salts that eventually clog radiator tubes. Also, the lack of abrasive silicates improves coolant pump seal life.
The initial aftermarket brand of Dexcool was Havoline Extended Life, but Prestone also now makes Dexcool. It's a licensed product and name, so just look for "Dexcool" on the label. I now use it in all my cars ranging from a '63 Corvette to a '91 MR2. I'll never use "green stuff" again.