Increase in energy demand, stringent emission norms and depletion of oil resources led to the discovery of alternative fuels forinternal combustion engines. Many alternative fuels like alcohols, petroleum gas, and compressed natural gas have been alreadycommercialized in the transport sector. In the present work, Pongomia oil and Neem oil are blended with diesel and used as analternate fuel for CI engines. The Pongomia oil and Neem oil can be converted into bio diesel using a chemical process of trans- esterification.Different proportions of fuel blends have been produced by the process of blending bio diesel consisting of 10%, 15%, 20%, 25%, and 30% (B10, B15, B20, B25, B30). The fuel properties of each blend are determined. The load test along with smoke and exhaust gas analysis of 4- Stroke Diesel engine using the blends of Pongomia oil and Neem oil with diesel are done in this study. The performance parameters of an engine are calculated for different blends. The sustainability of using alternate fuels in Diesel engines, especially the potential use of Pongomia oil and Neem oil as biodiesel have been brought to the fore through this work and suitable blends of bio diesel is suggested from the results.
 Keywords: 4-Stroke Diesel Engine, Pongomia and Neem oil Bo diesel, Performance, Smoke and exhaust gas analysis.