.Liquid lubricants are crucial to the successful development of advanced engines for the next decade. Engines are being optimized to meet emission standards as well as improved durability and fuel economy. New materials such as super alloys, ceramics and coatings offer an opportunity for better, more efficient engines. Lubricant research is focused on the severe environment and temperature requirements of a advanced engines with a top ring reversal temperature of over 400°C. This paper describes key lubricant considerations including oxidation and thermal stability, volatility, deposit formation, friction and wear control. Cooperative research efforts between industry and NIST resulted in several candidate high temperature liquid lubricants.