In most lubrication systems, oil comes into contact with air, metals, and high temperatures. These conditions are the primary causes of premature lubricant deterioration, leading to the formation of oxidation products, predominantly acids. Hydrocarbon oxidation in the liquid phase occurs via a radical chain reaction. The oxidation stability of lubricating oil is therefore critical for maintaining its performance during service.

In this study, dibenzyl-S-phenyl thioglyconitrile and its derivatives were synthesized using phase transfer catalysts and evaluated as antioxidants. These compounds were incorporated into oil at varying concentrations. The mechanism of action was studied by measuring the area occupied per molecule of additive in the oil phase. The antioxidant activity at different dosages was assessed, and a mechanism was proposed based on micellar behavior and thermodynamic considerations.

Oil oxidation was carried out over different time intervals, and degradation was monitored by measuring total acid formation. The oxidation stability of lubricating oil was found to be influenced by the sulfur and aromatic hydrocarbon content, with higher sulfur levels enhancing stability. The prepared compounds demonstrated superior oxidation stability compared to the imported standard compound (IRCANOX L 135–CIBA).