Every refrigeration system relies on oil to lubricate the compressor, and that oil must be compatible with the refrigerant. Mismatches cause poor oil return, compressor wear and failures — a critical consideration when retrofitting refrigerants.
Common oil types
- Mineral oil (MO) — used with older CFC/HCFC refrigerants like R22
- POE (polyol ester) — used with HFC and many HFO refrigerants such as R410A, R404A, R448A/R449A and R32
- PAG — common in automotive R134a/R1234yf systems
Why it matters in retrofits
When converting an older system (for example R22 to an HFC blend), the original mineral oil often isn’t compatible with the new refrigerant and won’t return to the compressor properly. An oil change to POE is frequently required — always check the refrigerant manufacturer’s guidance.
Good practice
Use the oil specified by the compressor and refrigerant manufacturers, keep POE oils sealed (they absorb moisture readily), and change filter driers when changing oil.
FAQ
Can I mix mineral oil and POE? Generally no — use the specified oil for the refrigerant, and flush or change oil during retrofits as advised.
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