In this study, preheated crude sunflower oil at 75 degrees C was used in a four-cylinder, naturally aspirated, indirect injection diesel engine. The experiments were conducted at the constant engine speeds under the full load condition of the engine to determine the performance, combustion, and injection characteristics of test fuels. The engine test results have been compared whiz the reference values that were determined by using petroleum-based diesel fuel. The results indicated that when the test engine was fueled with preheated crude sunflower oil, the brake thermal efficiency and brake specific fuel consumption increased by 1 and 5%, respectively, while brake power decreased by 1%. The cylinder gas pressure and the heat release curves of preheated crude sunflower oil appeared similar to those of petroleum-based diesel fuel. However, in detailed combustion analyses, it was found that the start of injection timing of preheated crude sunflower oil is earlier, its ignition delay is longer; and also its combustion duration is shorter than those of petroleum-based diesel fuel for all test conditions. The results of the emission test showed that when using the preheated crude sunflower oil, on average, unburned HC, CO, CO2 emissions, and smoke opacity decreased by 39, 6, 9, and 5%, respectively. Consequently, it was observed that, for a short term usage, the preheated crude sunflower oil presents satisfactory results in terms of engine performance and combustion characteristics.