In order to investigate the availability of citrus sinensis biodiesel in diesel engines, an experimental research was conducted. Citrus sinensis biodiesel was blended with conventional diesel fuel with volumetric ratios of 5%, 10% and 20%. Fuel properties of blends and pure citrus sinensis biodiesel were found out and performance characteristics and exhaust emissions of the engine fueled with blends were analyzed. The engine performance experiments indicated that citrus sinensis biodiesel cause a slight reduction in torque and brake power values. Exhaust emission tests revealed that while CO emission values decrease, NOX emission values increase with citrus sinensis biodiesel usage. To conclude, citrus sinensis biodiesel can be used as a very promising additive to improve CO emissions of conventional diesel fueled engine. (c) 2014 Elsevier Ltd. All rights reserved.