Oil is the generic name given to the products from petroleum refining that are liquid at ambient conditions, other products being heavy residues and bitumen which are solid at ambient conditions, and small quantities of gas and coke. Other mineral oils may be derived from coal.
Oil products are primarily characterized by their boiling range, with their specific properties determining their suitability for different applications. These may be finished products in their own right, after treatment to remove sulfur, etc., or as feedstock for further processing. Different oils need to have different properties and meet different quality criteria depending upon their ultimate use and, often, geographic destination. The nomenclature and specific properties needed reflect these requirements.
The lightest oils, termed gasolines, have a boiling range of C5 to approximately 90°C and are used primarily as a component of motor gasoline, or petrol Gasoline itself is not a high octane material, but is a mixture of several components which provide the desired properties of volatility and Octane Number etc. Thus, naphthas, boiling at approximately 90–160°C, are catalytically reformed to convert naphthenes into aromatics which contribute high octane gasoline components (see Hydrocarbons). Other high octane blending constituents are obtained from converting lighter materials (C3–C5 components) into different chemical species.
Typically, such products will be alkylates, isomerates, butyl and methyl ethers etc, the latter two compounds commonly known as TAME and MTBE, respectively. These components in particular have significantly reduced the use of lead based additives for enhancing octane number as a result of environmental pressures but with the attendant increase in processing costs. Straight run (unreformed) naphthas are also used extensively as chemical plant feedstock to produce a wide range of plastics.
Kerosene boils in the range 160–240°C and is primarily used as aviation fuel (Jet A-l). Although this fuel is required to meet numerous stringent property specifications, one of the critical properties is freezing point which effectively limits the highest boiling point components that it may contain. Fluid density is approximately 700 kg/m3 In some locations, kerosene is used as a burning fuel, in which case rather less stringent property specifications apply.
Gas oils boil up to approximately 360°C, with different types having different end points. The lightest products are used as diesel fuel and light heating oil, the heaviest used as components for industrial and marine fuel oils; heavy marine fuels also contain crude oil residues. Density and sulfur content are important properties, as are those properties affecting flow. In particular, diesel fuel needs to meet a cloud point specification which is an indication of the wax content and, thus, the ability to remain fluid in cold climates. Different specifications are used for different geographical locations and seasons.
Oils boiling up to approximately 500–550C° are used as lubricating base oils, from which, after extensive processing and treatment to control properties such as oxidation stability, color, wax content etc., a wide variety of finished lubricating oils are formulated. These oils are normally classified in terms of a viscosity range, an important property being the variation of viscosity over a given temperature range. To some extent this is a function of crude oil origin but processing criteria also has an effect.
The heaviest materials are oils of extremely high viscosity, virtually solid at ambient conditions, and are used for bituminous based products
Physical Principles of Oil Production, International Human Resources Development Corporation, Boston, USA ISBN 0-934634-07-6.