This analytical study examines the synergistic effects of (ZnO) Nano-particles as fuel additives on the performance and emission characteristics of conventional diesel engines. Various concentrations of ZnO nanoparticles, varying from (50 - 200 ppm), were systematically blended with standard diesel fuel using advanced homogenization techniques, including ultra-sonication and magnetic stirring. Experimental trials were conducted on a single-cylinder, four-stroke diesel engine operating at a constant rotational speed under variable load conditions. The findings reveal a significant improvement in combustion efficiency attributable to the catalytic properties and oxygen-enhancing effects of the Nano-particles, which promote more complete fuel oxidation. The optimal nanoparticle concentration of 200 ppm yielded a maximum increase in