This research studies variations in biodiesel upon addition of different concentrations of antioxidant and petrodiesel additives. Oxidation onset temperature, oxidation induction time, oxidative stability, thermal stability, crystallization onset temperature and moisture retention properties of the biodiesel, with and without antioxidants have been studied. Antioxidants like BHT, BHA, PrG, Vit E and Vit C were added to the biodiesel during the study. These samples were analyzed using the PDSC, TGA, DSC and TGA-SA instrumentation. The results of this research show an improvement in the OOT, OIT and Oxidative stability of biodiesel with the addition of antioxidants and by blending the biodiesel with different amounts of Petro-diesel. A significant improvement in oxidative stability of biodiesel has been observed with the addition of antioxidants and petrodiesel. There was no significant change noticed in the thermal stability, crystallization and the moisture retention properties of biodiesel. I hope that this research would help improving the oxidative stability of the biodiesel. The results from the analysis made in this study would also be helpful in designing a better antioxidant and aid in improving the present experimental methods for the OIT and thermal analysis.