This practical study examined the effect of engine torque on engine performance and emissions. The most important parameters of engine performance are thermal efficiency, brake power (BP), and specific fuel consumption. As for exhaust emissions, the most important of which are hydrocarbons (HCs), carbon monoxide (CO), and nitrogen oxides (NO_x). The experiment was conducted for a single-cylinder, four-stroke compression ignition engine. Mixtures (B0, B10, B20, B30, and B40) were taken from biodiesel prepared from sunflower oil by the esterification method. The engine speed was fixed at 1700 rpm, and torque variable was from 0 to 10 N m. The results indicated a decrease in engine BP by an average of 19.5 W, a decrease in thermal efficiency by an average of 1.058%, while an increase in fuel consumption by an average of 0.095 kg/kW h⁻¹ compared to diesel. As for exhaust emissions, HC emissions decreased by 5.8 ppm, while CO decreased by 0.0207%, and NO_x emissions increased by 138.5 ppm compared to diesel, due to changes in the properties of biodiesel, such as high density, viscosity, and low calorific value compared to the properties of regular diesel