Differential scanning calorimetry (DSC) has been used to evaluate the deposit-forming tendencies of ester lubricants containing alkali salts. In the temperature programmed oxidation test, sodium acetylacetonate (NaA), sodium perfluorobutyrate (NaPFB), potassium trifluoroacetylacetonate (KTFA), and sodium trifluoroacetylacetonate (NaTFA) are not only good antioxidation synergists for arylamine compounds such as p,p’-dioctyldiphenylamine (DODPA), but also effective deposit inhibitors. When combined with arylamine antioxidants, the salts can also effectively reduce the increases in viscosity, acid number and deposit formation of the ester oils in oxidation-corrosion tests.