With the SAE values (SAE International) they are signified by the standardized viscosity grades of automotive lubricants. Example: SAE 0W type is an extremely thin liquid winter oil. By contrast, SAE 40 indicates a thick summer oil. A multigrade oil, for example, SAE 0W-40 behaves in cold weather as SAE 0W and in heat as SAE 40. Thus, both the requirement criteria for cold start at low temperatures as well as hot highway driving at high temperatures is covered.
API Classifications ///
API = American Petroleum Institute (US standard). This Institute sets the world quality requirements and corresponding test criteria of motor oils. The classification is done separately for gasoline and diesel engines. S classifies gasoline engines (service classes, and Spark Ignition). C classifies diesel engines (commercial classes also Compression Ignition). The second letter represents the quality. For example SM LL (from 2004) features a high-quality oil for gasoline engines. CJ identifies oils for passenger cars with diesel engines from 2006 onwards.
ACEA Specifications ///
The ACEA (Association des Constructeurs Européens d'auto-mobile) defines since January 1996, the quality of engine oils according to European requirements. Car petrol engines have the designations A1-A5, passenger car diesel engines B1-B5. For diesel engines in commercial vehicles and general machinery, the symbols E1-E5 apply.
Example: (* xx is the year of introduction)
A1-xx = oils with fuel-saving properties
A3-xx * = heavy-duty engine oils
A4-xx * = GDI and FSI engine oils
A5-xx * = latest high performance engine oils
B = car diesel engine oil light-run class (B1-xx *, B3-xx *, B4-xx *, B5xx *)
C = car petrol and diesel engine oil with a particulate filter (C1-xx *, C2-xx *, C3-xx *, C4 * xx)
E = commercial vehicle engine oil (E4-xx *, E6 xx *, E7 xx *, E9 xx *)
Mineral Oils ///
Mineral oils are the longest known and used base oils. Mineral oils are inherently single-grade oils and can be produced relatively easily and inexpensively by the distilling and refining of petroleum. However, these oils are limited in their performance. Known viscosities: 15W-40, 20W-50.
Semi Synthetic Oils ///
As mineral oils and synthetic oils of petroleum are produced, only the manufacturing process (synthesis) is complex and expensive. Synthetic oils already bring innately a multigrade characteristic with them, so they can be handled much more economically with the use of viscosity index improvers. Due to their uniform structure, they respond better to the effectiveness of additives, so that it is possible to achieve better performance. Known viscosities for semi synthetic oils: 10W-40, 5W-30.
Fully Synthetic Oils ///
Fully synthetic engine oils can be used in gasoline and diesel engines and offer advantages over mineral oils, significant advantages include: improved cold start performance at low temperatures, optimized wear protection through faster supply at lubrication points, easy tracking, and excellent engine cleanliness. These oils usually meet the quality standards of the API, ACEA and corresponding company releases. Known viscosities: 0W-30, 0W-40, 5W-40.
When additives are oil-soluble, active ingredients which target the base oils are added to change or improve (chemically and / or physically effect) the properties of lubricants. The distinction between the additives is split into two categories, polar and nonpolar additives.
Polar Additives ///
Many additives are known as surface or surface-active agents, whose structure can be compared in principle to a match: like the head of a match, the active ingredients are concentrated, they are called the "polar group". It is as if water, acids and / or metals are attracted to the soot particles. This may form on the substances mentioned causing certain effects to happen (as they prevent bunching and retrieval, protect against wear and corrosion, neutralize acids). In comparison the stem of the match consists of a hydrocarbon radical, and only allows the solubility of the additive in the base oil.
Non-polar Additives ///
Other types of additives consist only of hydrocarbons with a special high molecular structure, these are non-polar. They are not attracted to water, acid, soot particles or metals, but only affect the oil.
Surface Protective Additives ///
The surface-protective additives include: detergents, dispersants, anti-wear, corrosion and rust inhibitors, friction modifiers.
High operating temperatures lead to deposits (lacquer, oil, carbon) especially in the piston area. This can lead to the seizure of the piston rings and thus increase blow-by gas quantities. Furthermore, deposits can also cause dragging of the piston on the cylinder bore. The result is mirror surface formation, also called "bore polishing" or plate form. Detergents prevent / reduce varnish and carbonaceous deposits and in addition have a cleansing effect.
Keep oil-insoluble with impurities finely distributed in the oil through a liquid suspension and thus prevent lumps of dirt particles (sludge).
Anti-foam Additives ///
Intense mixing of oil with air during operation causes foaming which leads to leakage of oil from the system (e.g. via ventilation points). Furthermore, it increases the speed of oil aging thus reducing viscosity and compressibility. The latter may in particular adversely affect hydraulic control operations. Antifoam additives (e.g. silicone, oil) prevent foaming and reduce the foaming tendency of oil. Foaming impairs the lubricants properties significantly.
Anticorrosive Additive ///
Corrosion is generally the chemical or electrochemical attack on metal surfaces. For corrosion protection there are preferably surfactant additives which can be ashless or ash reducing.
Antiwear Additives ///
By means of suitable additives extremely thin layers can be built on sliding surfaces, whose shear strength is substantially less than that of metals. Even under normal wear conditions (pressure, temperature) parts remain lubricated thus excessive wear (seizure or welding) is prevented.
Lubricating oils tend to oxidize (aging) under the influence of heat and oxygen. The decomposition process is further accelerated by acid reacting products in the combustion and traces of metals causing the catalytic effect (abrasive or corrosive wear). The addition of antioxidants results in significantly improved aging. Although you cannot eliminate the aging process completely, you can successfully slow it down.
Oil aging forms acids, varnish, resin and sludge-like deposits, most of which are oil insoluble, such as carbon. Antioxidants can act in three ways:
Radical scavengers (primary Antioxidants)
Peroxide scavengers (secondary aging substances)
Passivators / metal ion deactivators
Pour Point ///
Identifies the lowest temperature in degrees Celsius, where the oil will continue to flow. The "standstill" of oil is determined by the crystallization present in the base oil paraffins at low temperatures. Lower values are obtained by adding flow improvers.
Viscosity (flow behavior) is the property of a liquid to oppose a resistance to their reversible deformation. This plays an important role especially in engine oil. It is influenced by the temperature, pressure exerted on the lubricating film and the shear rate, i.e. the rate gap between the moving and fixed surface of a lubricating gap, for example in a warehouse.
Viscosity Index Improvers ///
Enables the production of multigrade engine oils. Increase VI improvers to stretch the viscosity of oil and thus improve the viscosity-temperature behavior. Figuratively speaking they are very long shaped molecules compressed in the oil during cold state where the movement of the oil molecules opposes a relatively low resistance. With increase in temperature, they uncoil themselves, occupy a larger volume and form a network of meshes, which slows the movement of the oil molecules and delay too rapid "thinning" of the oil.