Increased wear occurred in the actual refrigeration compressor when HFC refrigerants were substituted for CFCs to comply with the Montreal Protocol. A cause of this increased wear was believed to be the inferior extreme-pressure (EP) or antiwear capability of the alternative refrigerant HFC-134a as the environment gas, compared to that for CFC-I2 refrigerant which is currently used. However, under some severe conditions, it was found that the alternative also showed some antiwear or EP effect by forming a fluoride layer on a sliding surface.