The thermal degradation of a polyol ester lubricant used as the main component of textile fiber finishes at high temperature (i.e., 220 °C) has been studied to model the real-world degradation of finishes on fiber manufacturing equipment. Chemical and physical analyses were performed on the thermally stressed lubricants using a combined analytical technique to measure the progress of degradation in the lubricant. The effects of two commonly used antioxidants in the fiber industry and two secondary arylamine antioxidants used in turbine engine oil on the thermal behavior of the lubricants were investigated. Phenyl-α-naphthylamine (PAN) shows a significant improvement in the thermal stability of the lubricant used in this study and could be considered as a potential fiber finish antioxidant for the textile industry.