 Ionic liquids, IELs, are room-temperature molten salts that offer advantages as lubricants due to their ability to protect against wear and reduce friction in various systems, and can be incorporated into non-polar base oils with excellent performance. IELs consist of large asymmetrical ions that readily adsorb onto metal surfaces and form a protective film under boundary lubrication conditions, while certain compounds can react to form a protective tribofilm under extreme pressure conditions. This article was authored by Anthony E. Summers, Patrick C. Howlett, Douglas R. McFarlane, and others.