Heats of immersion were determined for three base oils, their fractions as separated by polarity, and model compounds on a 52 100 steel surface. The method consists of calculating the heat of immersion based on surface tension and contact angle measurements made at temperatures from 25°C to 175°C. Friction and wear tests were performed on the same oils using micro-sample four-ball wear tests. The heat of immersion data were found to be inversely proportional to friction and wear. Model compounds with different functional groups similarly tested, however, suggest molecular structures have a significant role in influencing friction and wear when chemical reactions become the dominant lubrication mechanism rather than adsorption.