To obtain novel structural antioxidants that have different antioxidant mechanisms, four 2-(alkylthio)-N-(4-(phenylamino)phenyl)acetamides 2a–d as dual functional antioxidants are designed, synthesized, and confirmed by 1H-NMR, FTIR, MS, and elemental analysis. The antioxidant behavior of compounds 2a–d as additives of base oil triisodecyl trimellitate (TIDTM) is evaluated by non-isothermal and isothermal DSC analyses. The results showed all compounds can greatly increase the incipient oxidation temperature (IOT) and oxidation induction time ...