Biodiesels derived from microalgae oil promise to be an alternative for the conventional diesel fuel due to their similarity in properties. In this present work, Ce-Ru-O catalysts are used as an additive to the NOME in the form of an emulsion. A single-cylinder, four-stroke direct injection compression ignition engine is made to run on B20+CeO2, and B20 dozed with different dosage levels of Ce0.95Ru0.05O2, Ce0.9Ru0.1O2, and Ce0.8Ru0.2O2 microemulsions. Ce-Ru-O at different concentrations is used to study the effect of metal oxide on emission characteristics of the fuel. Experimental results show that addition of microemulsion has a positive effect on emission characteristics and also acts as an oxidation catalyst.