Nanofluids are suspensions of nanoparticles mixed in liquids and show significant enhancement in some thermophysical and combustion properties of the resulting suspension. In this study, the changes in the performance and emissions characteristics of a conventional diesel engine are verified experimentally using the combustion of a mixture of nanofluid (water and Al₂O₃) and conventional Iraqi diesel fuel. The nano-Al₂O₃ (51 nm diameter) was used in this study; multiple weight ratios of this nanoparticle were mixed with water to form a nanoparticle suspension. The weight fractions used were 1%, 3%, 5%, 7%, and 10%. After that, a fixed volume ratio of the resulting suspension (10%) was added to the diesel and completely mixed. The results indicate that the addition of the nano-alumina-water suspension has increased the brake thermal efficiency up to 5.5%, and reduced the relative fuel consumption up to 3.94%, compared to diesel fuel. In the analysis of emitted exhaust emissions, CO, HC, NOx, PM and noise emissions, they were found to be lower than diesel fuel, while CO₂ emissions increased.