Turkey's economy is mainly dependent on agriculture and the country provides almost all petroleum demand through imports, the evaluation of vegetable alternative engine fuels is of great importance. In this study, usability of methyl ester of rapeseed oil and hazelnut produced abundant in Turkey was examined. Experiments were carried out in a four-cylinder, four-stroke, 46 kW, direct injection diesel engine. A comparison of diesel fuel, the rapeseed oil methyl ester and the hazelnut oil methyl ester blends was made from the engine performance and emissions point of view. Engine performance and emission tests were carried out with 4 different fuel that 100% diesel (SD), 50% rapeseed oil methyl ester and 50% diesel (B1), 50% hazelnut oil methyl ester and %50 diesel (B2), 25% rapeseed oil methyl ester, 25% rapeseed oil methyl ester and 50% diesel (B3). Highest engine performance and lowest specific fuel consumption were obtained with SD fuel. But the use of biodiesel led to reduction in CO and smoke emissions accompanying with the imperceptible torque loss. As the rapeseed methyl ester rate increased in the blend, smoke and CO emissions decreased, NOx and CO2 emissions increased. With the use of B1 fuel, NOx emissions increased up to 7.2%. (C) 2012 Elsevier Ltd. All rights reserved.