Reduction of CO2 emission from diesel engine is necessary because of requirement in atmospheric environment. To reduce diesel fuel consumption of a general purpose diesel engine, blend alcohol composed of 87% ethyl alcohol was supplied with two methods. One is a mixing of the blend alcohol with diesel fuel and the other is a port injection of the blend alcohol. Engine performance was measured with combustion analysis based on cylinder pressure and a dynamometer. The mixing of the blend alcohol with diesel fuel was limited less than 7% because of separation and boiling resistance. The port injection of the blend alcohol was limited about 25% in fuel by means of knocking during engine operations. In comparison with diesel fuel, combustion is faster with higher thermal efficiency in the former case and combustion is delay in the latter case without any reduction on thermal efficiency. The port injection is better than the mixing to reduce diesel fuel consumption.
