Grease is a semisolid liquid that consists of a liquid lubricant mixed with a thickener. The oil does the lubricating while the thickener holds the oil and provides a resistance to flow. Soaps (a metallic element such as lithium, calcium, sodium, or aluminum reacted with a fatty acid) or fine particles of a lubricating additive, such as polytetrafluoroethylene (PTFE) or lead are used as thickeners in the grease.
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