This study investigates the performance and emission characteristics of a single-cylinder, four-stroke, direct-injection diesel engine using various biodiesel and hydrocarbon blends. The experimental analysis focused on evaluating the effects of different fuel blends, specifically B20, B20C8, and B20C8A, on engine performance, brake specific fuel consumption (BSFC), brake thermal efficiency (BTE), and emissions including hydrocarbons (HC), smoke opacity, nitrogen oxides (NOx), and carbon monoxide (CO). The B20C8A blend, consisting of 20% biodiesel, 8% octane, and 72% diesel with antioxidants, demonstrated the most significant improvements. Results indicated that B20C8A achieved the lowest BSFC values, highest BTE, and significant reductions in HC, NOx, smoke opacity, and CO emissions compared to conventional diesel (D100) and other blends. This study highlights the potential of optimized biodiesel-hydrocarbon blends to enhance engine performance and reduce environmental impact, providing a viable alternative for cleaner and more efficient diesel engines. © 2024 Elsevier B.V., All rights reserved.