This study was conducted to determine the rates of mineral oil oxidation and organometallic compound formation at temperatures approaching those existing in concentrated contacts. The thin-film microreactor was used so that diffusional effects could be analyzed and quantified. This allowed the calculation of rate coefficients for the oxidation reaction. These rate coefficients were then used in a kinetic model of the four-ball wear tester to predict film thickness in concentrated contacts. Presented at the 38th Annual Meeting in Houston, Texas, April 24–28, 1983