By  the  methods  of thermal analysis there were  investigated the intermediate and final products of  the synthesis of multifunctional additives IKhP-150 and IKhP-156 which are highalkaline carbonated calcium salts of the products of condensation of alkylphenol with formaldehyde and amino-acetic or p-aminobenzoic acids. It has been found that termooxidative stability of the investigated additives reaches 360⁰C. It was shown that additives synthesized by variant of stage condensation of alkylphenol with formaldehyde and aminoacetic or p-aminobenzoic acids possess the highest thermostability and antioxidative efficiency in comparison with additives obtained by variant of joint condensation. The investigated for comparison commercial additives ВНИИНП-714 and MACK yield to the additives IKhP-150 and IKhP-156 by thermooxidative stability