Mineral oil is any of various colorless, odorless, light mixtures of higher alkanes from a mineral source, particularly a distillate of petroleum, as distinct from usually edible vegetable oils.
The name 'mineral oil' by itself is imprecise, having been used for many specific oils over the past few centuries. Other names, similarly imprecise, include 'white oil', 'paraffin oil', 'liquid paraffin' (a highly refined medical grade), paraffinum liquidum (Latin), and 'liquid petroleum'.
Most often, mineral oil is a liquid obtained from refining crude oil to make gasoline and other petroleum products. Mineral oils used for lubrication are known specifically as base oils. More generally, mineral oil is a transparent, colorless oil, composed mainly of alkanes and cycloalkanes, related to petroleum jelly. It has a density of around .
Some of the imprecision in the definition of the names used for mineral oil (such as 'white oil') reflects usage by consumers and merchants who did not know, and usually had no need of knowing, the oil's precise chemical makeup. Merriam-Webster states the first use of the term "mineral oil" as being 1771. Prior to the late 19th century, the chemical science to determine the makeup of an oil was unavailable in any case. A similar lexical situation occurred with the term "white metal".
"Mineral oil", sold widely and cheaply in the United States, is not sold as such in the United Kingdom. Instead, British pharmacologists use the terms "paraffinum perliquidum" for light mineral oil and "paraffinum liquidum" or "paraffinum subliquidum" for somewhat more viscous varieties. The term "paraffinum liquidum" is often seen on the ingredient lists of baby oil and cosmetics. British aromatherapists commonly use the term "white mineral oil". In lubrication, mineral oils make up Group I, II, and III base oils that are refined from petroleum.
The World Health Organization classifies minimally treated mineral oils as carcinogens group 1 known to be carcinogenic to humans; Highly refined oils are classified group 3 as not suspected to be carcinogenic, from known available information sufficient to classify them as harmless.