Tribological Study Comparing PAG and POE Lubricants Used in Air-Conditioning Compressors under the Presence of CO2 Academic Article uri icon


  • Polyalkylene glycol (PAG) and polyolester (POE) synthetic lubricants are good candidates for air-conditioning systems that work with alternative refrigerants such as carbon dioxide (CO2). Both synthetic lubricants are widely used in air-conditioning compressors and have been optimized for use with hydrofluorocarbon (HFC) refrigerants. However, it is still not clear which lubricant is more suitable for use in compressors operating with CO2as a refrigerant. This study compares the performance of PAG and POE lubricants of the same viscosity (ISO VG 68) used in air-conditioning compressors. The materials used were Al390-T6 disks and hardened steel SAE 52100 pins. The tests were performed using a high pressure tribometer (pin-on-disk configuration) in the presence of CO2. The results showed that scuffing and wear resistance of Al390-T6 tested with PAG were superior compared to the samples tested with the POE lubricant. Chemical analysis using X-ray photoelectron spectroscopy showed that PAG tends to promote the formation of carbonate layers on the surface, leading to improvement in the tribological performance of the interface. © 2008 Society of Tribologists and Lubrication Engineers.

author list (cited authors)

  • Nunez, E. E., Demas, N. G., Polychronopoulou, K., & Polycarpou, A. A.

citation count

  • 11

publication date

  • September 2008