Abstract A detailed study of Tables III and IV, in which the effect of chemical agents on high temperature aging are evaluated by relaxation and oxygen absorption indexes and conventional test indexes, shows a much higher evaluation consistency for the Table III indexes and presents some doubt regarding the significance of the data given in Table IV and Figure 8. Although the conventional tests have the advantage of speed and convenience, the difficulties of obtaining truly significant correlation between laboratory aging tests and practical performance are considerable. The methods reported in this paper may, therefore, be of value in supplementing the numerous aging tests already in use in various laboratories.