Changing energy regulations urge all appliance manufacturers to use more efficient components in their products. Reciprocating compressor is one of the most crucial part for the energy efficiency of a refrigerator. Not only electrical and thermodynamic but also mechanical efficiency is the crucial issue determining the coefficient of performance (COP) of a compressor. Therefore, precise and trustworthy measurement comprising the frictional losses is one of the critical parameters to anticipate the real effect of novel design concepts. The objective of this study is the development of a new approach to measure mechanical losses of a reciprocating compressor. The method is based on the precise measurement of deceleration. A test rig, where the oil temperature, ambient pressure and temperature are able to be adjusted, is established. Measurements are performed under different average load for varying oil viscosity level. Load conditions are provided by adjusting ambient pressure of the chamber in which compressor body is placed. A heater is used on the body of the compressor to simulate temperatures corresponding with real temperatures acquired from the measurements of the compressor. Compression work is calculated by measurement of absolute cylinder pressure with respect to angular position of the crank shaft. Results are promising to use this measurement system for more detailed investigation.