Relation between Base Oil Composition and Oxidation Stability at Increased Temperatures

Abstract

The sources of crude oil have become more uncertain, therefore, the quality of base oils may fluctuate. The authors have been studying the effects of base oil composition changes on oxidative stability. The long range goal is to develop a laboratory procedure to predict changes in Automatic Transmission Fluid performance with variation in base stock composition. In this initial study, the compositions often commercially available base oils, plus ten mixtures made from them, have been characterized by NMR and IR spectroscopy and their high temperature (180 C) oxidation rates determined. The relative oxidation stability, as measured in a glassware oxidation test without catalyst, was found to be most sensitive to the sulfur and aromatic content of the base oils. A correlation between composition parameters and oxidation rate has been derived.