One of the many technical benefits of green diesel (GD) is its ability to be oxygenated, lubricated, and adopted in diesel engines without requiring hardware modifications. The inability of GD to reduce exhaust tail emissions and its poor performance in endurance tests have spurred researchers to look for new clean fuels. Improving gasohol/hydrogen blend (GHB) spark ignition is critical to its long-term viability and accurate demand forecasting. This study employed the Response Surface Methodology (RSM) to identify the appropriate GHB and engine speed (ES) for efficient performance and lower emissions in a GHB engine. The RSM model output variables included brake specific fuel consumption (BSFC), brake thermal efficiency (BTE), hydrocarbon (HC), carbon dioxide (CO2), and carbon monoxide (CO), while the input variables included ES and GHB. The Analysis of Variance-assisted RSM revealed that the most affected responses are BSFC and BTE. Based on the desirability criteria, the best values for the GHB and the ES were determined to be 20 and 1500 rpm, respectively, while the validation between experimental and numerical results was calculated to be 4.82. As a result, the RSM is a useful tool for predicting the optimal GHB and ES for optimizing spark-ignition engine characteristics and ensuring benign environment. © 2022 ASTM International. All rights reserved.