Why is mixing refrigerants generally avoided?

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Mixing refrigerants is avoided because each refrigerant is designed to work with specific materials, seals, and lubricants inside a system. When different refrigerants are blended, the resulting mixture can behave unpredictably and may not stay uniform as the system operates. This can cause chemical incompatibilities with the lubricating oil and with components like gaskets, elastomers, and metals, leading to degraded seals, oil foaming or separation, improper lubrication, and even corrosion. These issues can raise discharge temperatures and pressures, reduce efficiency, and risk compressor damage. Because the blend's properties are uncertain and not approved for the equipment, service and safety become compromised, and the refrigerant may have to be discarded or specially reprocessed. So the primary concern is chemical incompatibilities with lubricants and system materials, which is why mixing refrigerants is generally avoided.