This experiment work is to investigate the performance parameters of single cylinder, four stroke engine connected to eddy current dynamometer fuelled with argemone biodiesel and blend with diesel fuel under different load condition (0%, 20%, 40%, 60%, 80%, 100%) and constant engine running speed. The performance parameters consist of brake power (BP), brake thermal efficiency (BTHE), and brake specific fuel consumption (BSFC). The argemone mexicana oil was used for production of biodiesel. The transesterification process was used for production of argemone oil methyl ester by using methanol in the presence of sodium metal as a catalyst. The process undergoing various reaction conditions with molar ratio (1:6, 1:3, 1:9 oil to methanol), reaction time (60 min, 90 min, 120 min), reaction temperature (55°C, 65°C, 75°C, 85°C) and catalyst (1%, 1.5%, 2%, 2.5% w/w of oil) effects the fuel properties of argemone biodiesel. The most favorable conditions for transesterification of argemone oil with methanol in the presence of sodium metal as a catalyst was found with molar ratio 1:6 (oil to methanol), reaction time 120 min, reaction temperature 75°C and catalyst 1.5% (w/w of oil). The fuel properties were calculated and compared with Diesel. The result shows that argemone biodiesel blend (AB10 and AB20) have improved fuel property and brake thermal efficiency, brake power and specific fuel consumption value closer to diesel value.