Abstract : 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