Biodiesel is one of the most important renewable energy sources for diesel engines. Studies have been carried out on different kinds of renewable fuels such as raw vegetable oil, waste cooking oil and biodiesels derived from various vegetable oils. In addition research on biodiesel has gained momentum in recent years because of the increasing environmental issues caused by fossil fuels and depletion of oil reserves. However, problems such as high viscosity, low lower heating value and increase in NOx emissions due to oxygen content are limiting the. scope of biodiesel application. JP-8 is a kerosene-based aviation fuel. JP-8 is a strategically important fuel due to properties such as lower cold filter plugging point and high lower heating value. There are some application problems on existing internal combustion engines because of the low cetane number of JP-8. In this study, diesel, sunflower methyl ester and JP-8 fuel blends are tested in a direct injection diesel engine and the possibility of the use of biodiesel and JP-8 together is investigated. As a result of tests carried out at full load conditions, engine performance and exhaust emissions are compared with those for diesel fuel. By using 25% JP-8 and 75% sunflower methyl ester, engine torque decreased by 3% and brake specific fuel consumption increased by 3.9%. Although it has been ascertained that the NOx emissions increased, smoke emissions decreased. As a result it has been determined that biodiesel and JP-8 can be used together.