The effects of temperature on the lubricity of a number of lubricants are studied. An apparatus designed to study lubricants under boundary conditions, with provisions for varying temperature, load, and speed, is described. Sharp transitions from smooth sliding to severe galling and seizure are observed at a specific temperature which is characteristic of the lubricant and the test conditions. These “failure temperatures” are useful in understanding the lubrication mechanism and in predicting lubricant performance.Presented as an American Society of Lubrication Engineers per at the Lubrication Conference held in Atlantic City, N.J., October, 1956.