Biodiesel fuels are an alternative to diesel fuel. Biodiesel is an oxygenated, sulphur free, non-toxic, biogradable and renewable fuel. It is derived from vegetable oils. Since straight vegetable oils have quite high viscosity compared to mineral diesel, they have to be modified to bring their combustion-related properties and viscosity closer to mineral diesel. This is done by modifying their molecular structure through a transesterification process. In the present study, a military heavy duty 38.8 liter, 585 kW supercharged, compression ignition diesel injection (CIDI) engine was fuelled with diesel, Karanja oil methyl ester (KOME) biodiesel, and KOME biodiesel with cerium oxide fuel additive, respectively. These were subjected to 100 hours long term endurance tests. Lubricating oil samples, drawn from the engine fuelled with these fuels after a fixed interval of 20 hours, were subjected to elemental analysis. Atomic absorption spectroscopy was done for quantification of various metal debris concentrations. Lubricating oil samples were also subjected to ferrography test which indicated lower wear debris concentrations for a biodiesel with fuel additive operated engine. Number of tests was conducted in order to evaluate the comparative performances of these fuels such as lubrication measurement, density measurement, viscosity measurement, total base number etc. The experimental result showed that engine performance with Karanja oil biodiesel with fuel additive increased by 5%, along with lower gaseous emission including 14% - 25% lower NOx emission, and lower total particulate number concentration, as compared to diesel fuel The performance of biodiesel fuel is found to be superior to that of diesel oil. Also, the lubricating oil life is found to be longer while operating the engine on biodiesel with fuel additive. Engine metals wear were found 26% lower for a KOME biodiesel with cerium oxide fuel additive operated engine.