This document provides a study of oil lubricant – refrigerant effects in the performance of a hermetic compressor. For that, it is presented here one method for the thermodynamics properties which is based on the departure functions and the Peng-Robinson equations of state. Furthermore, for the thermodynamic calculations on the compressor (such as power consumption, heat loss, among others) a semiempirical model, based on the empirical characterization of the compressor, available on the literature, was utilized. At the end of this work, a quantitative analysis on the influence that the mass concentration of lubricant has on the compressor performance, such as discharge temperature, mass flow of the mixture, is presented.