Heating and cooling of the gas are unavoidable events associated with compression and expansion in reciprocating compressors. an obvious result of this is the transfer of heat from and to the gas which also occurs in an unsteady manner. such a transfer has both advantages as well as disadvantages. this investigation is concerned with the improving efficiency of two stage reciprocating air compressor by providing water cooling source, radiator coolant and ethylene glycol. the experiments of a two-stage double-cylinder reciprocating compressor system with air, water and different intercoolants were performed. the equations representing the volumetric and isothermal efficiency were solved in the predicted results compared with the experimental data and theoretical data of water, other cooling sources and air cooling showing good agreement