This paper present a comparative study of performance and emission characteristics of compression ignition engine with different method of using straight vegetable oil. Single cylinder water cooled, constant speed diesel engine which is generally used for water pump or generator sets is used for investigations. During tests, engine is operated with petrodiesel, vegetable oil (at normal room temperature and at 90°C) and vegetable oil-ethanol emulsions at room temperature. The engine performance parameters and emissions are measured at different test fuels from no load to full load conditions.