MP39 is a blend: HCFC R-22, HCFC R-124, HFC R-152a.

Blends are not welcome in automotive refrigerant systems, since few a/c repair shops will touch such a system. It'll contaminate recovery machines, which a/c shops depend on to stay profitable.

Plus, you still have to change the lubricant in the system from mineral oil to alkylbenzene. So why go with MP39 if you can convert to r134, which costs the same as MP39, plus you have to flush the old lubricant from the system anyhow? I see no advantage to using MP39.

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95 E320 Cabriolet, 169K