In this study, the effect of the antioxidant additives on the oxidation stability of biodiesel and the exhaust emissions of a diesel engine has been studied. Biodiesel used in this study was produced via transesterification process from canola oil, and was blended with diesel fuel 20% by volume (B20). Antioxidant additives butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), tert-butylhydroquinone (TBHQ) and 2-ethylhexyl nitrate (EHN) were individually dissolved at concentrations of 0, 500, 750 and 1000 ppm by weight in B20 fuel blend for experiments. The test results of oxidation stability showed that the effectiveness of the antioxidants was in the order of TBHQ > BHA > BHT > EHN. According to exhaust emissions test results, antioxidant additives had quite effects on oxides of nitrogen (NOx), carbon monoxide (CO) and hydrocarbon (HC) emissions of diesel engine running on biodiesel. A 1000 ppm concentration of EHN additive was optimal as NOx levels were substantially reduced in the whole engine speed in comparison with B20 fuel. (C) 2014 Elsevier Ltd. All rights reserved.