G Global warming due to the use of refrigerants that are not environmentally friendly in air conditioning systems, encourages researchers to conduct research to find alternatives to alternative refrigerants of HFC type. The direct replacement model of refrigerant in HFC R134a and hydrocarbon type refrigerants has been widely developed. Retrofit refrigerant in air conditioning machines (AC) is not known with certainty the optimal pressure on the compressor, which has an impact on the evaporation temperature and performance of the air conditioning machine. This study aims to determine the effect of evaporation temperature on the performance of air conditioning machines using refrigerants R134a and MC 134 at the optimal refrigerant filling pressure. The parameters observed in this study are the effect of optimal pressure on the compressor, condenser temperature, evaporator temperature, cooling load on the performance of the refrigeration engine. Experimental research is still carried out on a laboratory scale. From the research results, it is found that the optimal refrigerant filling pressure for refrigerant R134a occurs at a pressure of 20 bar-g, and for refrigerant MC134 at a pressure of 25 bar-g. At the evaporation temperature between 22.3°C-25.3°C, the refrigeration effect is 106.43% greater, the compressor work increases by 70.22%, the heat absorbed by the evaporator increases by 5.99%, the heat discharged by the condenser increases by 2, 78%, compressor power decreased by 12.4%, electric power decreased by 14.69%, COP increased by 21.37% after using hydraulic refrigerant on MC 134.