lubricating oil
Quick Summary
Lubricating oil is a substance, often derived from petroleum or fatty oils, used to reduce friction and wear between moving surfaces. This process, known as lubrication, has been employed since prehistoric times, with early lubricants including mud and animal fats. The 19th century saw crude oil become the primary source for lubricants, leading to significant improvements in machinery speed and capacity.12
Lubrication can occur in three basic ways: fluid-film, boundary, and solid. Fluid-film lubrication involves a complete separation of surfaces by a liquid or gas film. Boundary lubrication occurs when surfaces are in partial contact, with friction determined by surface and lubricant properties beyond viscosity. Solid lubricants, such as graphite or molybdenum disulfide, are used in extreme conditions.2
Viscosity is a key property for classifying lubricating oils, with different applications requiring varying levels of viscosity. Multigrade oils, for example, are designed to maintain effective lubrication across a range of temperatures. Additives like antioxidants and detergents further enhance performance by maintaining engine cleanliness and preventing corrosion.3
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