Increasing in the energy demand there is a need of alternate fuels. The main important aspects of biodiesel are biodegradable, renewable energy resources. In current scenario many researcher are inventing new methods and idea of preparing biodiesel products. In this papers its explains candlenut biodiesel mixed with different proportions of cerium oxides (CeO<inf>2</inf>) nanoparticles in variable compression ratio engine. The main purpose of adding the nanoparticles is to enhance the better combustion and good emission characteristics in a diesel engine. The candlenut biodiesel blends of B20 and B40 is mixed with cerium oxides nanoparticles at 25 ppm added to the blended fuel to find out performances and emission levels in the diesel engine. The results show improvement in the carbon monoxide of B40 whereas B20 there is slight reduction in the Nox, HC& smoke opacity. © 2023 Elsevier B.V., All rights reserved.