Presently diesel generation against consumption is seen as the problem for future. Therefore the alternative is required to be found out. Biodiesel is found the potential resource as an alternative to diesel. The present automobile industry which uses 100% diesel is to be replaced by the blend of diesel & biodiesel. The various biodiesel blends study is carried out & particularly for Palm-based biodiesel blends with petrodiesel is considered for the study. The present work is to study the engine performance & exhaust emission for optimum blend ratio of above-mentioned biodiesel petrodiesel blends. The experiments will be carried out & the result will be shown. The pure petrodiesel (100%) and blend ratio of 5%, 10%, 15%, 20%, 25%, 30%and 35% will be taken for experiment. The literature says that the optimum blend ratio for biodiesel and petrodiesel is around 20%. The exhaust emission will also be studied. Care is taken during work, the existing engine should work with the suggested blend ratio and should give good engine performance and the exhaust emission should be minimum or within a tolerable limit.