Oil

A bottle of olive oil used in food

An oil is any substance that is in a viscous liquid state ("oily" state) at or slightly above ambient temperatures, and is both hydrophobic (immiscible with water, literally "water fearing") and lipophilic (miscible with other oils, literally "fat loving"). Thus oils are nonpolar substances.

The general definition of oil includes classes of chemical compounds that may be otherwise unrelated in structure, properties, and uses. There are many types of oils, including vegetable oils, petrochemical oils, and volatile essential oils. They are used for food, fuel, lubrication, and the manufacture of paints, plastics, and other materials. Specially prepared oils are used in some religious ceremonies as purifying agents.

Etymology

First attested in English 1176, the word oil comes from Old French oile, from Latin oleum, which in turn comes from the Greek ἔλαιον (elaion), "olive oil, oil" and that from ἐλαία (elaia), "olive tree", "olive fruit".</ref> The earliest attested forms of the word are the Mycenaean Greek e-ra-wo and e-rai-wo, written in the Linear B syllabic script.

Types

Organic oils

Organic oils are produced in remarkable diversity by plants, animals, and other organisms through natural metabolic processes. Lipid is the scientific term for the fatty acids, steroids and similar chemicals often found in the oils produced by living things, while oil refers to an overall mixture of chemicals. Organic oils may also contain chemicals other than lipids, including proteins, waxes (class of compounds with oil-like properties that are solid at common temperatures) and alkaloids.

Lipids can be classified by the way that they are made by an organism, their chemical structure and their limited solubility in water compared to oils. They have a high carbon and hydrogen content and are considerably lacking in oxygen compared to other organic compounds and minerals; they tend to be relatively nonpolar molecules, but may include both polar and nonpolar regions as in the case of phospholipids and steroids.

Mineral oils

Crude oil, or petroleum, and its refined components, collectively termed petrochemicals, are crucial resources in the modern economy. Crude oil originates from ancient fossilized organic materials, such as zooplankton and algae, which geochemical processes convert into oil. The name "mineral oil" is a misnomer, in that minerals are not the source of the oil—ancient plants and animals are. Mineral oil is organic. However, it is classified as "mineral oil" instead of as "organic oil" because its organic origin is remote (and was unknown at the time of its discovery), and because it is obtained in the vicinity of rocks, underground traps, and sands. Mineral oil also refers to several specific distillates of crude oil.^{[citation needed]}

Applications

Food oils

Several edible vegetable and animal oils, and also fats, are used for various purposes in cooking and food preparation. In particular, many foods are fried in oil much hotter than boiling water. Oils are also used for flavoring and for modifying the texture of foods (e.g Stir Fry).

Health advantages are claimed for a number of specific oils such as omega 3 oils (fish oil, flaxseed oil, etc) and evening primrose oil.

Trans fats, often produced by hydrogenating vegetable oils, are known to be harmful to health.

Oil as fuel

Most oils burn in air generating heat which can be used directly or converted into other forms of energy in the usual ways. Oils are used as fuels for heating, lighting (such as a kerosene lamp), powering combustion engines, and other purposes. Oils used for this purpose nowadays are usually derived from petroleum (including fuel oil, diesel oil, and gasoline), though biological oils such as biodiesel are also used.

Lubrication

Synthetic motor oil.

Given that they are non-polar, oils do not easily adhere to other substances. This makes them useful as lubricants for various engineering purposes. Mineral oils are more suitable than biological oils, which degrade rapidly in most environmental conditions.

Manufacture of petrochemicals

Crude oil can be processed into plastics and other substances.

Heat transport

Many oils have higher boiling points than water and are electrical insulators, making them useful for liquid cooling systems, especially where electricity is used.

Painting

Color pigments can be easily suspended in oil, making it suitable as supporting medium for paints. The slow drying process and miscibility of oil facilitates a realistic style of painting. Oil paints have been used since the fifteenth century.

Religion

A jar of consecrated oil. Etched into the glass are the letters "OS" for Oleum Sanctum, Latin for holy oil.

Oil has been used throughout history as a religious medium. It is often considered a spiritually purifying agent and is used for anointing purposes. For example, holy anointing oil has been an important ritual liquid for Judaism and Christianity.

Massage

Oil allows massage strokes to glide along the skin. The oil is selected based on the viscosity for the type of massage being conducted. A relatively high-viscosity oil such as almond oil may be used for a luxuriant, slow style; a lighter oil such as grape seed oil may be selected for a rapid approach. Scents may also be added.

Environmental concerns

Petroleum is considered a nonrenewable resource, and burning it produces carbon dioxide, a greenhouse gas. Biological oils are renewable and do not produce net carbon dioxide, but require land to grow. Both also produce pollutants such as nitrogen oxides (NO_x).

Oil spills are the unintentional release of a liquid petroleum hydrocarbon into the environment as a result of human activity. Petroleum-based hydrocarbons can negatively impact marine life and seabirds even at low concentrations. Oil that is denser than water settles on and penetrates the seabed, and it may take months or even years to clean up. Some methods to clean up an oil spill include the use of bioremediation, dispersants, dredging, and skimming.

References

ISBN links support NWE through referral fees

• Alberts, Bruce, Rebecca Heald, Alexander Johnson, David Morgan, Martin Raff, Keith Roberts, and Peter Walter. Molecular Biology of the Cell. W. W. Norton & Company, 2022. ISBN 978-0393884821
• Conaway, Charles F. The Petroleum Industry: A Nontechnical Guide. Tulsa, OK: PennWell Pub. Co., 1999. ISBN 0878147632
• Gunstone, Frank D.. Vegetable Oils in Food Technology: Composition, Properties, and Uses. Chemistry and Technology of Oils and Fats. Osney Mead, Oxford: Blackwell, 2002. ISBN 0849328160
• Gunstone, Frank D. The Chemistry of Oils and Fats: Sources, Composition, Properties, and Uses. Oxford, UK: Blackwell Pub., 2004. ISBN 0849323738
• Raymond, Martin S., and William L. Leffler. Oil and Gas Production in Nontechnical Language. Tulsa, OK: PennWell Corporation, 2006. ISBN 1593700520

External links

All links retrieved September 22, 2025.

• Oil and petroleum products explained US Energy Information Administration
• Oil Types NOAA Office of Response and Restoration
• All About Oil Union of Concerned Scientists

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