This document investigates the use of Al2O3 nanoparticles as an additive to compressor oil in vapor compression refrigeration systems (VCRS). Experimental tests were conducted adding Al2O3 nanoparticles to PAG oil at concentrations of 1.5%, 1.7%, and 1.9% by mass. Results showed that the coefficient of performance (COP) of the VCRS improved by 19.14%, 21.6%, and 11.22%, respectively, compared to using pure oil. The maximum COP and refrigeration effect occurred at a concentration of 1.7% Al2O3 nanoparticles. Theoretical COP and system capacity were also highest at this concentration. Therefore, adding Al2O3 nanoparticles to compressor oil,