The authors aimed to investigate the fuel-atomization, combustion, and exhaust emissions characteristics of dual component fuels. The analysis revealed that the blending of diesel or bioethanol fuel slightly affected the reduction of the spray tip penetration and had little influence on the variation of the spray cone angle. The droplet size of biodiesel fuel was reduced by blending with diesel or bioethanol fuel with low kinematic viscosity and surface tension. Regarding the combustion characteristics, B80D20 fuel had the same combustion characteristics as B100. However, the blending of bioethanol fuel with biodiesel fuel caused an extension of the ignition delay and a decrease of the peak combustion pressure. There was little difference in the exhaust emissions characteristics caused by the blending of diesel fuel. However, EI-NOx emissions were reduced significantly by the blending of bioethanol fuel. However, EI-HC and EI-CO emissions were increased by blending the bioethanol fuel.