This study delves into the performance and emission characteristics of dual-fuel diesel engines that utilize mahua seed biodiesel (MSB) in conjunction with methane gas disinfection into the consumption diverse. Our primary objective is to determine whether baseline diesel engines may be made more efficient and pollutant-free through the use of methane fumigation. The diesel fuel test mainly aimed to collect performance baseline indicators in a typical operating environment. Keeping the test running at a constant speed of 1500 rpm while subjecting it to varied loads allowed us to next examine the engine’s efficiency and emissions. Next, the engine was fed methane gas through MSB at 3 and 5 LPM (liter/min) flow rates. Brake thermal efficiency (BTE) improved by 29.86% at 3 LPM, and heat release rate (HRR) increased by 46.54% at 5 LPM, according to the data. A total of 48.4 and 73.5% reduction in carbon monoxide (CO) emissions, 25.12% in hydrocarbons (HC) emissions, and 34.56% in smoke opacity were observed related to diesel at complete load. At a 3 LPM flow rate, NOx emissions were 37.86% greater than diesel, and at a 5 LPM flow rate, they were 58.42% higher. The addition of methane gas to mahua seed biodiesel improves engine performance and decreases emissions, suggesting that it could be a good substitute for diesel fuel. The significance of investigating alternate fuels to diesel engines in reducing pollutants and making diesel engine operations more sustainable is highlighted by this research.