Biodiesel is one of the potential alternate source of energy, various policies are now been implemented, in the urge for more and more production and utilization of biodiesel. In the parallel context, lot of research is been done to identify and prove the feasibility of these oils, but one place were the biodiesel production process if finding itself in trouble is in identifying its properties, which vary drastically with temperature and petro-diesel blending. In this research work, two most prominent biodiesels based on Jatropha Oil and Palm Oil were taken and their thermo-physical properties viz. density, viscosity, refractive index, flash point and calorific value in variation with temperatures at 298.15 K, 303.15 K, 313.15 K, 318.15 K and 323.15K and blend fraction between pure diesel and pure biodiesel with consecutive 5% variations (B0, B5, B10, B15, B20, B25, B30, B35, B40, B45, B50, B55, B60, B65, B70, B75, B80, B85, B90, B95, B100) were determined and correlations were generated. Further, the effect of these biodiesels on engine performance and exhaust emissions were studied using an IC Engine. The optimized results is at petro-diesel in blend with 20% biodiesel.