In this experimental study, the fuel system of the OM364 diesel engine manufactured by IDEM company, which operates in the basic mode with inline fuel pump and mechanical governor control, is upgraded to a common rail system with electronic control by the ECU. Also, emmssion of exhaust gases is reduced by SCR and DOC catalysts then performance and emmission parameters of engine are compared in two cases. The base engine of OM 364 with Euro 2 emission standard is upgraded to Euro 5 EEV emission standard after changing the fuel system to common rail and after refining the exhaust gases with SCR and DOC catalysts. The important point is to pass the Euro 5 EEV standard without using DPF in exhaust gas refining, which reduces the cost of car manufacturers.