Freeze12 really isn't a good alternative for R12 as it's 80% R134. IF your going to go that route, you may as well convert to R134 and be done with it.

I have used R406a in my 280SEL. It is the only drop in replacement that I know of for R12 as it can mix with the oil. It turned my fingers blue while it was in there, but it appears that I had a leak in the system and as a result, it didn't last very long. I guess I need to replace the compressor and 34 year old hoses.

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With best regards

Al