In a modern day world alternative source of energy are given importance due to gradual depletion of fossil fuels reserves vegetable oils can be used as an alternative to diesel in CI engines. In the initial stage the tests are conducted on the four stroke single cylinder water cooled direct injection diesel engine with constant speed by using diesel and base line data is generated by varying loads. In second stage, experimental investigation has been carried out on the same engine with same operating parameters by using the Ethyl Esters of Mahua oils in different proportions as M10, M20, M30, and M40 to find out the performance and emission parameters. The performance and emission parameters obtained by the above are compared with the base line data by using diesel and optimum mahua oil blend is obtained. The performance and emission parameters measured from the above tests are to be compared with diesel base line data and optimum blend M20.