Biodiesel is an alternative fuel for Diesel engines made from new/used vegetable oils and animal fats. It is bio-degradable and has lower hydrocarbon emission levels and similar performance characteristics compared to conventional Diesel fuel. After modifying its molecular structure through a transesterification process, biodiesel (rapeseed oil methyl ester – RME) can be used as an alternative fuel in compression ignition engines without any modification. Modern internal combustion engines must have longer oil drain periods to decrease operating costs and environmental pollution levels. Related studies indicate that biodiesel fuel has a potential for reducing engine wear. This experimental study investigates the effect of commercial Diesel fuel and RME on lubricating oil performance and the exhaust emissions. Performance, emissions and long-term wear tests were carried out and discussed on a single cylinder marine Diesel engine for both Diesel fuel and 100 % RME. Results indicated that the RME has a deteriorating effect on lubricating oil performance by decreasing oil viscosity degree and base number. Ferrous element is the main evidence of the engine wear and it was increased depending on lowering viscosity relating to the fuel dilution and rising running period. Although carbon monoxide and hydrocarbon pollutants in exhaust gas decreased with RME, nitric oxides raised significantly as well as performance results which remained similar except for specific fuel consumption.