Refrigerant Oil Mixing: Best Practices & Guidelines

Key Points:

• Proper oil return is essential for compressor lubrication and protection.

• Modern refrigeration systems primarily use POE (polyolester) and PVE (polyvinyl ether) oils.

• Older systems often used MO (mineral oil) or AB (alkylbenzene) with R22.

• Oil mixing is possible but should not exceed 5-10% of the total oil volume.

• Leftover oil must be free of contaminants and acids to avoid system damage.

• Proper flushing, nitrogen brazing, and vacuuming (below 1000 microns) are necessary for oil transition.

Refrigerant Oil Mixing Guidelines

Oil return is critical for compressor longevity and system efficiency. As the industry transitions to synthetic oils like POE and PVE, questions arise about mixing these with older oils like MO or AB when replacing refrigerants or compressors.

Can Oils Be Mixed?

Yes, but with limitations. Industry standards recommend that any remaining old oil in the system should not exceed 5-10% of the total oil volume. While a small amount of residual oil is generally safe, ensuring the leftover oil is clean and free of acid or contaminants is crucial.

Steps for Proper Oil Transition:

1. Drain & Replace: Remove as much old oil as possible before adding new oil.

2. Flush the System: If contamination is suspected, flush the system thoroughly.

3. Brazing with Nitrogen: Prevent oxidation and acid formation by brazing with nitrogen.

4. Deep Vacuuming: Evacuate to 1000 microns or less to remove moisture and residuals.

Following these steps ensures a smooth oil transition and prevents long-term system damage.