Overconsumption of fossil fuels has accelerated global warming and raised environmental air pollution levels. Recent studies have looked into the potential use of alternative, environmentally friendly fuels for diesel engines in response to the rising need for oil. Biodiesel is a renewable alternative fuel that is environmentally friendly. The significant increase in nitrogen oxide (NOx) emissions is the most notable disadvantage of biodiesel. This study examined the effect of antioxidant-treated Jatropha biodiesel on the performance and exhaust emission parameters of a VCR diesel engine. For this study, diesel, Jatropha biodiesel (B30), and phenolic antioxidant additive diphenylamine at 100 ppm are added by weight to the B30 blend named as B30 + DPA fuel blend was used. A hybrid RSM was used in conjunction with CCD and MCDM approaches such as AHP and COPRAS techniques to produce a sustainable model to derive the most accurate optimum models for output responses. From experimental findings, the antioxidant significantly reduced NOx emission. The inclusion of DPA in the tested blend lowered the average NOx emissions and brake-specific fuel consumption (BSFC) by 7.4% and 7.8%, respectively as compared with B30. Also, the brake mean effective pressure (BMEP) of B30 + DPA is 5.01% and 0.38% higher than diesel and B30, maximum cylinder pressure (CPMax) is 0.9% higher than B30, but 3.4% lower than diesel. The optimal setting of engine input parameters is recorded at compression ratio of 15, 7.5% EGR-HOT, and 12 kg load, for optimum BP, BMEP, BSFC, CPMax, and NOx emissions. Therefore, the B30 + DPA blend is suitable for enhancing diesel engine performance and minimizing exhaust emissions.