In order to examine how the determined induction periods in the RSSOT are affected when a steady-mass approach is followed, the grease samples were re-run under TP-3 test conditions but this time the PTFE dish was filled with 5g of each grease (approach B). Figure 10 shows the difference in the preparation of the sample to be examined under the steady volume vs. steady mass approach. The results that were obtained from the steady-mass approach are presented in Figure 11 and compared with the corresponding measurements from the steady volume determinations. Though the 5g sample preparation results in a relatively larger outer surface of the sample that is in direct contact with the oxygen, the lower mass appears, in general,
to give rise to elongated induction period. At low IPs, i.e. ≤ 100 min, the determinations were not significantly affected by the quantity of the sample employed and the results were comparable between the two approaches. On the other hand, as the relative oxidation stability increases, considerably higher induction periods are generated at the 5g sample approach. This indicates that the quantity of the sample that is inserted in the PTFE dish plays an important role in the time that is needed to achieve the pre-determined breakpoint of the test. Nevertheless, the fixed mass approach doesn’t seem to substantially alter the observed order of stability of the tested greases compared to the fixed volume approach. The corresponding IPs are plotted in Figure 10 (b) and with the