This document discusses lubricants used in thermal power plants. It begins by introducing the importance of selecting the proper lubricant and understanding lubrication theory. It then discusses the fundamentals of lubrication in reducing friction and wear. Different types of lubricating oils and their characteristics like viscosity and additives are explained. Common additives are outlined that improve performance by interacting with machine metals. Grease composition and characteristics are also covered. The document concludes by examining lubricant specifications for steam turbines and other thermal power plant equipment.