Differential scanning calorimetry (DSC) and oxidation-corrosion tests were employed to evaluate the inhibition of pentaery-thritol ester containing sodium perfluorobutyrate (C3F7COONa) towards oxidation. The results show that C3F7COONa enhances antioxidancy of p,p'dioctyldiphenylamine (DODPA). The changes occurring to DODPA in the oxidation of esters, with and without C3F7COONa, were followed by mass (GC/MS) chromatography (MC). The proposed mechanism of the inhibition involves a synergy between alkali metal salts and arylamines. Although DODPA does not react directly with the alkali salt, the salt still functions within the antioxidation mechanism of DODPA. When DODPA reacts with free radicals to form alkyl and hydroxy substituted benzoquinonemonoimine compounds (with mass to charge ratio M/Z, 422), the alkali metal ion can participate and produce a new intermediate product having high antioxidant activity; this intermediate product serves as the main antioxidant, long after the depletion of DODPA. This process may involve a reaction between alkylphenylamino alkylphenol and the alkali metal ion. The intermediate product is believed to be the salt of alkylphenylamino alkylphenol.