In some high-temperature applications, it is desirable to deliver the lubricant as a thin liquid film without recirculation. For these conditions, the buildup of the deposit on the hot surfaces outside the actual bearing contact area can be a problem. In this study, a mathematical model is developed which incorporates several chemical and physical processes which are taking place when a thin liquid film of lubricant is converted to a deposit at elevated temperatures. Specifically, the model utilizes kinetic studies of the degradation of tricresyl phosphate and the evaporation of this lubricant at modest temperatures, <280°C, and modest levels of TCP degradation to predict the final or terminal amount of deposit which will be produced over a broad range of temperature. The key to this model is incorporating the influence of the evaporation of the liquid lubricant on the diffusion of oxygen in the gas phase. The diffusion of the evaporated lubricant molecules away from the liquid phase inhibits the diffusion of the oxygen in the gas phase. Consequently, the oxidation of the liquid lubricant is significantly reduced by the unavailability of oxygen even when the liquid film is exposed to a moving stream of air.Presented at the 48th Annual Meeting in Calgary, Alberta, Canada May 17–20, 1993