Lubricants are substances introduced between two surfaces in relative motion to reduce friction, wear, and heat generation. They play a critical role in environmental chemistry because their use and disposal have significant implications for ecosystems, particularly in terms of soil and water contamination. The mechanism by which lubricants operate involves the creation of a thin film that separates surfaces, preventing direct metal-to-metal contact. This film can be boundary, hydrodynamic, or elastohydrodynamic in nature, depending on the operating conditions and load applied. In boundary lubrication, the lubricant molecules form a monomolecular layer adhering to the surfaces, which is especially important under high-load or low-speed conditions. In hydrodynamic lubrication, the moving surfaces are fully separated by a continuous lubricant film, generated by the relative motion of the surfaces themselves. Elastohydrodynamic lubrication occurs in highly loaded contacts, such as in gears or rolling bearings, where the lubricant film thickness is influenced by the elastic deformation of the contacting surfaces. The classification of lubricants can be broadly divided based on their physical state, chemical composition, or application. Physically, lubricants are classified as liquids, semi-solids, or solids. Liquid lubricants, such as mineral oils, synthetic oils, or bio-based oils, are the most commonly used and can flow easily to form a continuous film. Semi-solid lubricants, including greases, consist of a thickener dispersed in a base oil, providing excellent adhesion and resistance to water washout. Solid lubricants, such as graphite, molybdenum disulfide, and polytetrafluoroethylene (PTFE), are employed in extreme conditions where liquid lubricants fail, including high temperatures or vacuum environments. Chemically, lubricants can be mineral-based, derived from petroleum, or synthetic, produced through chemical synthesis to achieve specific performance characteristics such as oxidation stability, viscosity control, and thermal resistance. Bio-lubricants, derived from plant oils, are gaining attention for their biodegradability and reduced environmental toxicity. Lubricants also contain various additives to enhance their performance. Anti-wear additives, such as zinc dialkyldithiophosphate (ZDDP), form protective films on metal surfaces to prevent direct contact. Extreme pressure (EP) additives,