AbstractThis paper compares the performance of polyol ester base fluids — in key areas such as miscibility, stability, transport property, and antiwear protection — with other candidate oils proposed for use with HFC‐134a and with naphthenic oils conventionally employed with ozone‐depleting CFC refrigerants such as CFC‐12. The data demonstrate that properly selected polyol ester‐based fluids meet key lubricant requirements for use with ‘ozone friendly’ refrigerant HFC‐134a. In addition, the paper describes key issues in retrofitting existing CF C/naphthenic oil‐based systems to run with HFC‐