The challenge of improving the efficiency and sustainability and reducing emissions of diesel engines through the use of different fuel blends− such as diesel, biodiesel, and fuel blends mixed with TiO 2 nanoparticles− is addressed by this research. The study investigates how the performance, emissions, and sustainability aspects of a one-cylinder, four-stroke, water-cooled diesel engine are impacted when 50 and 100 ppm of titanium dioxide (TiO 2) nanoparticles are added to various blends of diesel and biodiesel under varied engine loads ranging from 25% to 100%. The addition of TiO 2 nanoparticles leads to reductions in brake specific fuel consumption (BSFC) of up to 8% with B0 and up to 14.29% with B15, improvements in energy efficiency of up to 2% with B0 and up to 4.02% with B15, and improvements in exergy efficiency of up to 1.88% with B0 and up to 3.77% with B15. With regard to hydrocarbon (HC) emissions, the use of TiO 2 nanoparticles decreased emissions by up to 18.4% at the cost of nitric oxide (NO) emissions, which increased by up to 5.87%. The exergy performance coefficient (Ex p) and sustainability index (SI) increased by up to 18.99% and 5.63%, respectively. The percentage changes showed enhanced engine performance, lower emissions, and improved energy conversion efficiency with the inclusion of TiO 2 nanoparticles. The results suggest fuel blends' advantages in terms of energy conversion; however, it is also important to look at the economic feasibility and stability of TiO 2 nanoparticles.