Oil and Lubricant
Oil is a relatively thick, viscous liquid produced from crude oil, plants, animals, or chemical synthesis. Oil and water don’t mix (usually). A lubricant is any substance that serves to reduce friction between moving parts. There is a lot of overlap between the two.
Most oils are lubricants. The oil creates a layer of liquid that prevents contact between solid surfaces, which dramatically reduces friction. But not all oils are lubricants:
- Vegetable oil is used in cooking, to soften and flavor food and as a heat transfer medium.
- Dielectric oils, which fill electrical transformers, are used to carry away heat and insulate against electrical arcing.
- Hydraulic oil is a power transfer medium in heavy machinery, so you have oil in a hose instead of a drive shaft or electrical wire (although lubricity is usually also important in hydraulic systems).
Most lubricants are oils. The chemical properties of oil — low volatility, high lubricity, low freezing point — make it excellent for use as a lubricant. But not all lubricants are oils:
- Teflon coatings reduce sliding friction and sticking in mechanisms (and cookware). This is longer-lasting than a film of oil.
- Graphite powder is a dry lubricant used where liquid lubricants are undesirable or unreliable, like lock mechanisms and mechanical clocks. Liquids add viscous drag to small moving parts.
- Grease is usually made from oil, but is thickened into a paste or gel consistency so it will stay in place and not run off of parts.