ABSTRACTBiodiesels produced from microalgae oil guarantee to become a substitute for the typical diesel fuel for their similarity in characteristics. In this research, the efficiency, combustion as well as exhaust emission properties of single-cylinder, four-stroke, air-cooled as well as direct injection compression-ignition engine had been examined at constant speed of 1500 rpm under full-load condition when it is powered with different blend ratios like 80% diesel +20% algae oil biodiesel (B20), 80% diesel + 20% algae oil biodiesel + 25ppm RuO2 (B20 + 25ppm), 80% diesel + 20% algae oil biodiesel + 50ppm RuO2 (B20 + 50ppm), 80% diesel + 20% algae oil biodiesel + 75ppm RuO2 (B20 + 75ppm), 80% diesel + 20% algae oil biodiesel + 100ppm RuO2 (B20 + 100ppm). Adding RuO2 nanoparticles with the B20 improved the maximum cylinder pressure as well as heat release rate values when compared with diesel and B20. The final results of exhaust emission indicated a reduction in HC, CO and also smoke opacity pollutants, while enhanced NOx emission. Also, the outcomes showed that the BSFC reduced as well as BTE improved. Ruthenium oxide blends give greater results than B20 and diesel fuel in several aspects, like better combustion cylinder pressure, lesser brake specific fuel consumption and also less CO pollutants.