In this investigation, the surface characteristics of Nickel based superalloy Inconel-625 were evaluated by the electrical discharge machining with used cooking oil-based biodiesel as a dielectric. Nickel-based superalloys find wide applicability in numerous industries due to their specific properties. The Cu electrodes of various densities prepared by atomic diffusion additive manufacturing process were used for machining. A comparison of the performance was made based on average surface roughness. The Design-expert software was used for experimental design and parametric analysis. The outcome demonstrated that bio-dielectric fluid produced improved surface characteristics. The surface roughness was observed to reduce. The surface micrograph obtained from scanning electron microscopy also confirms a better surface finish of bio-dielectric fluid over EDM oil. The surface roughness was shown to be most significantly influenced by the discharge current, with the other parameters having little or no effect. The results showed that for bio-dielectric, the lowest Ra was 0.643 µm, and for EDM oil, the highest value of 0.844 µm. The slightest difference in roughness value for two dielectric fluids was 0.013 µm, and the highest difference was 0.115 µm.