The synthesis of fatty acid methyl esters (FAME or biodiesel) and paraffin in a non-thermal plasma Dielectric Barrier Discharge (DBD) reactor has produced satisfactory results. Plasma technology has shown advantages over conventional method by synthesizing biodiesel without the presence of catalysts, requiring relatively low energy, and not producing glycerol as a by-product. This research aims to compare the FAME and paraffin produced from used palm oil, with and without added castor oil. In this study, the triglycerides are reacted with methanol in the plasma DBD reactor. The reactor is operated at atmospheric pressure, liquid feed flow rate of 1.3 mL/s, argon gas flow rate of 25.27 mL/s, and plasma voltage of 10.2 kV AC. The independent variables in this study are sources of triglycerides and output frequency of the Electronic Power Transformer (EPT). Characterization of the produced biodiesel includes GC-MS, GC-FAME, density, and viscosity. The optimal condition for biodiesel conversion reaction in a DBD plasma reactor from this study is at a reaction temperature of 40 °C and a 1:1 molar ratio of oil to methanol, and a reaction time of 120 minutes.