Figure 3 shows the ECT of oil containing heptyl sulfide.
The ECT of additive-free oil increases and exceeds 500 pC/ml
after 100 h of heating. However, small increases in the ECT
are detected for both BTA-added oil and DBPC-added oil.
The ECT values are less than 50 pC/ml during the thermal
aging tests. Both BTA and DBPC have almost the same
suppression effect on ECT for the oil containing the sulfide