The Effects of Fuel Combustion Products on Antioxidant Consumption in a Synthetic Engine Oil

Abstract

The rates of the antioxidant consumption in a synthetic oil used in various engines were found to be normalized when plotted vs. the product of engine firing events and the surface area of the oil film per cylinder. This suggests that the antioxidant consumption occurs primarily in the piston-cylinder area of an engine. The pulse flame generator was used to determine the specific effects of combustion products on the antioxidant decay. The rate of antioxidant consumption in a synthetic engine oil has been followed as a function of flame-oil distance and the concentrations of nitric oxide, carbon monoxide, and unburned hydrocarbons in the combustion products of isooctane and air. The results suggest that the diffusion of free radicals formed in the fuel combustion event into the oil film is an important process in the antioxidant decay in engines.

Determination of the High Temperature Antioxidant Capability of Lubricants and Lubricant Components

“…Used Engine Oils. In previous investigations (Korcek et al, 1979(Korcek et al, ,1981Mahoney et al, 1980) the peroxy radical titration method (Mahoney et al, 1978) was used to follow the decay of low-temperature antioxidant capacity in used engine oils. That method yielded information on residual content of radical-trapping inhibitors.…”

“…A procedure for determining the radical-trapping antioxidant capacity of new and used lubricants was published previously (Mahoney et al, 1978). That method provides useful information and has been applied to investigations of antioxidant consumption in engine oils during laboratory and service evaluations (Korcek et al, 1979(Korcek et al, ,1981; Mahoney et al, 1980;Murray et al, 1982; Hsu et al, 1982). The method, however, measures only radical-trapping capacity at low temperature and, thus, does not reflect the contribution of peroxide-decomposing species or natural inhibitors that can be formed from oil components during oxidation; these types of species can play important roles at elevated temperatures.…”

Kinetic approach to engine oil. 1. Analysis of lubricant transport and degradation in engine system

“…Analysis of Lubricant Degradation (A) TAN (Total Acid Number). Engine oil can be oxidized in the piston-cylinder area even during the induction period of the oxidation in an oil sump as demonstrated by Mahoney et al (1980). As Figure 4 shows, eq 10 and 11 hold for increasing TAN, A, during the induction period.…”

Lubricating Oil Oxidation and Stabilisation

“…The importance of thin film oxidation at high temperatures was demon strated by Mahoney et al [110] who found that antioxidant consumption occurred primarily in the piston-liner area of an engine and by use of a laboratory pulse-flame generator, showed that rapid consumption of antioxidants in the engine oil occurred when the oil was exposed to the products of combustion of iso-octane.…”