I'm not sure but I think this post went into two different directions. Larry's initial post mentioned "environmentally friendly anti-freeze". DexCool is toxic which is not classified as "environmentally friendly".

I do not have any experience with environmentally friendly anti-freeze but I do have experience with DexCool. I have used DexCool in my non-Mercedes cars for the past 2 years with no gelling. The jug of DexCool states that with a 50/50 mixture with a pressure cap at 15psi it is good down to -34 Deg. F. This does not however state what the temperature rating is with the radiator cap off or sitting in the jug which would be at a higher temperature.

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Ray
1998 Mercedes E320, 200K Miles
2001 Acura 3.2TL, 178K Miles
1992 Chevy Astro, 205K Miles