The effect of ethanol on diesel engine performance using B30 fuel has been investigated, namely a mixture of 30% calophyllum inophyllum biodiesel and 70% petrodiesel. The ethanol concentration mixed to B30 was 10% and 20% vol/vol. The experiment was conducted on a single-cylinder four-stroke diesel engine with a natural air system and joined with a generator that functioned as a dynamometer. The test was applied three times to the machine for each load, involving 0, 200, 400, 600, and 800W at a constant rotation speed of 2000 rpm. The experiment reveals that the consistent engine speed method and lamp load produce the same torque (Nm) and effectiveness power (kW) between fuels, impacted by the governor's mechanism. The 20% ethanol (B30E20) has the highest effective thermal efficiency of 28.41% and effectiveness fuel consumption of 0.46 kg/kWh. The addition of 20% ethanol reduced exhaust emissions of carbon monoxide and hydrocarbons up to 0.09% and 27.33 ppm. However, there was an exhaust emissions increase of carbon dioxide up to 8.0%. The exhaust emissions increase of carbon dioxide cannot be considered as a negative consequence because it can be reused (consumption) in the photosynthesis process raw material biofuels.