• Engine performance and emissions of a single-cylinder diesel engine are studied • The fuel was modified with a blend of orange peel oil methyl ester and nanoparticles • The results showed modified fuel achieved better performance and exhaust emissions • The BTE of BC15 and BC25 showed a 4% and 23% increase over the diesel fuel data • The improved combustion characteristics and the good cetane rating for OPOME Due to the increasing cost of crude oil, the depletion of this resource has prompted researchers to look into the various potential applications of renewable fuels. Biobased fuels have the potential to reduce the harmful effects of fossil fuels. Here, the Biodiesel extracted from the orange peel can be used as an economical alternative fuel. A metal oxide nanoparticle called cerium oxide was added to an orange peel oil methyl ester to study its impact on the diesel engine. Biodiesel is mixed with cerium oxide nanoparticles (CeO 2 ) nanoparticles using an ultrasonicator and a magnetic agitator to ensure that the particles are homogeneous and achieve uniform suspension. The higher surface area/volume ratio of the nanoparticles allows them to perform better combustion and emission characteristics. This Study showed that the brake thermal efficiency of the test fuel was significantly improved by 12% compared to diesel fuel. The Study revealed that the CeO 2 nanoparticles could act as an oxygen shelter for combustion. Its surface energy content has a considerable volume ratio that accelerates the combustion process. Results of an experiment revealed that nanoparticles could reduce emissions. Compared to conventional fuels, biodiesel fuel produced by using CeO 2 nanoparticles exhibited an improvement in various emissions. The performance parameters of a biodiesel blend with a cerium oxide nanofluid additive were improved by 27%, 6.5, and 7% compared to 20% of the Biodiesel fuel mixture in NOx, CO, and smoke emissions. This reveals that the CeO 2 nanoparticles could be the ideal oxidizing catalyst for reducing the emissions of H.C. and C.O.