Antioxidant kinetics in synthetic lubricants field testing

With the increases in engine performance, lubricants technology has quickly made great strides. The selection of mineral base oils has become more stringent, and the use of synthetic lubricants has been an important feature, allowing better perfonnance characteristics, among which is longer drain periods.1,2. These evolutions have not led to the elimination of performance additives, which must be included in the composition of every engine lubricant. Among these, antioxidants play a prominent part: they participate in the protection of the lubricant against degradation b y oxidative agents. The ways in which they act are complicated and not entirely understood even today: essentially the initiator, ie oxygen from air, reacts with the lubricant to form peroxides, and then radicals which are themselves secondary oxidative agents. According to the chemical structure of the antioxidant additives, a break in these chain reactions can occur. Thus it is important to select the best compounds for each lubricant: this can be achieved by experimentation and by specific identification of the antioxidant agents which are used.