I just changed my system from R134a to Duracool R12a. It seems to be really good so far, although I might have to tweak my system a bit.... It was doing 5C at the sensors in my 95 S320. It was 27C according to my outside temp sensor...
With R134a, the lowest reading I got after checking it with the same sensors was 10C.... It was only 20C outside that day... I was never impressed with R134a. It's all but impossible to buy the small quick fill cans of it here in Canada anyways. The local small town family owned hardware store even stocks duracool here....

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All it takes for evil to prevail is for good men to stand by and do nothing.

Too many people tip toe through life, never attempting or doing anything great, hoping to make it safely to death... Bob Proctor

'95 S320 LWB
'87 300SDL
'04 E500 wagon 4matic