Tetrazole derivatives can be synthesized by direct synthesis from either trialkyltin azide and nitrile compound of sodium azide and nitrile compound. However the synthesis of tetrazole derivatives especially alkyl tetrazole by using nitrile containing an electron releasing substituent reacted more readily with trialkyltin azide than with sodium azide. Subsequent tetrazole products were obtained by treatment with hydrogen chloride and identified by spectroscopic techniques (IR, NMR and MS) Tetrazole derivatives are effective in increasing cetane number only when used in a concentration of 0.05 % by weight. The antiknock property was determined by cetane number and cetane index. They are easy to blend with diesel fuel by organic solvent helping refiners to upgrade diesel fuel qualitatively and economically.