Lubricating Oils

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Infobox on Lubricating Oils
Example of Lubricating Oils
Lubricating oil.jpg
Origin -
Stowage factor (in m3/t) 1,47 m/t (drums)
Humidity / moisture See text
Ventilation -
Risk factors See text

Lubricating Oils


Motor oil or engine oil is an oil used for lubrication of various internal combustion engines. The main function is to lubricate moving parts; it also cleans, inhibits corrosion, improves sealing, and cools the engine by carrying heat away from moving parts.

Motor oils are derived from petroleum-based and non-petroleum-synthesized chemical compounds. Motor oils today are mainly blended by using base oils composed of hydrocarbons, polyalphaolefins (PAO), and polyinternal olefins (PIO), thus organic compounds consisting entirely of carbon and hydrogen. The base oils of some high-performance motor oils however contain up to 20% by weight of esters.

Most motor oils are made from a heavier, thicker petroleum hydrocarbon base stock derived from Crude Oil, with additives to improve certain properties. The bulk of a typical motor oil consists of hydrocarbons with between 18 and 34 carbon atoms per molecule. One of the most important properties of motor oil in maintaining a lubricating film between moving parts is its viscosity. The viscosity of a liquid can be thought of as its "thickness" or a measure of its resistance to flow. The viscosity must be high enough to maintain a lubricating film, but low enough that the oil can flow around the engine parts under all conditions. The viscosity index is a measure of how much the oil's viscosity changes as temperature changes. A higher viscosity index indicates the viscosity changes less with temperature than a lower viscosity index.

Motor oil must be able to flow adequately at the lowest temperature it is expected to experience in order to minimize metal to metal contact between moving parts upon starting up the engine. The pour point defined first this property of motor oil, as defined by ASTM D97 as "... an index of the lowest temperature of its utility ..." for a given application, but the "cold cranking simulator" (CCS, see ASTM D5293-08) and "Mini-Rotary Viscometer" (MRV, see ASTM D3829-02(2007), ASTM D4684-08) are today the properties required in motor oil specs and define the SAE classifications.

Oil is largely composed of hydrocarbons which can burn if ignited. Still another important property of motor oil is its flash point, the lowest temperature at which the oil gives off vapours which can ignite. It is dangerous for the oil in a motor to ignite and burn, so a high flash point is desirable. At a petroleum refinery, fractional distillation separates a motor oil fraction from other crude oil fractions, removing the more volatile components, and therefore increasing the oil's flash point (reducing its tendency to burn).

Another manipulated property of motor oil is its Total Base Number (TBN), which is a measurement of the reserve alkalinity of an oil, meaning its ability to neutralize acids. The resulting quantity is determined as mg KOH/ (gram of lubricant). Analogously, Total Acid Number (TAN) is the measure of a lubricant's acidity. Other tests include zinc, phosphorus, or sulfur content, and testing for excessive foaming.

The NOACK volatility (ASTM D-5800) Test determines the physical evaporation loss of lubricants in high temperature service. A maximum of 15% evaporation loss is allowable to meet API SL and ILSAC GF-3 specifications. Some automotive OEM oil specifications require lower than 10%.

See also Bulk Oils and Fats

Shipment / Storage / Risk factors

Lubricating oils are shipped in bulk and in drums.

Loss of volume usually occurs from oil adhering to tank and pipeline walls or from incomplete emptying of tanks; this will increase with multiple transhipments. The higher the viscosity of the oil the greater the possibility of loss. Different methods of measurement may lead to inaccuracies between shipped and delivered volumes. Lubricating oils should be clear and bright and free from water, sediment and other impurities. A water content of 0,01% to 0,02% will make oils cloudy. Only a very small amount of water will actually dissolve in oil, the remainder being insoluble and making the oil cloudy. Solubility of water increases with temperature, and therefore, oil which is cloudy at low temperatures may be clear at normal or higher temperatures. Cloudy oil can be clarified, generally by heating. Contamination by fresh water may be caused by condensation entering with oil from land tanks, through condensation in ship’s tanks or by incomplete pumping out of ballast or cleansing water. Removal of sea water can be a costly process involving filtering of the oil. Contamination by other oils necessitates, in most cases, an expensive redistillation process. Loss of volume will be higher when discharge takes place in low temperature conditions. Engine lubricating oils are usually shipped in 1 liter plastic bottles. Claims may be advised suggesting breakage by way of splitting of the bottles and, as such, loss of contents. In such cases the specific location of the damaged bottle in the carton and the location of the carton in the pallet should be identified. The exercise should relate to each damaged bottle throughout. On the information obtained it should then be possible to identify if the damage was caused by some incident in transit, by incorrect stowage or if the individual containers are defective. Sample containers should be withdrawn and be held for specification test if it is suggested that they were defective. Usually the empty plastic bottles are inspected on arrival at the bottling plant. The bottles are produced in moulds (referred to as cavities) and would usually have been checked from an example of each cavity by weight and neck dimension. The bottles should then be top load tested to ensure that the minimum specification (on a 1 liter pack) of 20 g is met. The specification is based on 1,5 times the dead weight loading of the anticipated pallet configuration.