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Major foreign oil companies in the past have been based on the nature and processing of crude oil into the base paraffinic base oil, intermediate base oil, naphthenic base oil. Since the 1980s, the development of engine oil for the pilot, low viscosity lubricants tend, multi-level, universal, viscosity index base oils to put forward higher requirements, the original base oil classification methods have been unable to meet this a change in trend. Therefore, the major foreign oil companies now generally classified according to the size of the viscosity index, but has been no strict standards. API base oil in 1993 will be divided into five categories (API-1509), and and as EOLCS (API engine oil licensing certification system), and its classification in Table -1.
Table -1 API-1509 base oil classification criteria
Test methods ASTM D2007 ASTM D2270 ASTM D2622/D4294/D4927/D3120
Category Saturated hydrocarbon content I/% Viscosity IndexVI Sulfur content/%(Quality Score)
ClassI <90% 80~<120 >0.3
ClassII >90% 80~<120 <0.3
ClassIII >90% >120 <0.3

Poly olefin α-(PAO)


All non-I, II, III or IV base oils

Group I base oils are usually obtained by a conventional "three old" process production system, from the production process, the production process of Group I to the basic physical process of oil-based, hydrocarbon structure does not change, the quality of base oil production depends on the content and nature of the feedstock ideal components. Accordingly, such base oils is limited in performance.
Class II base oil is through a combination of process (solvent hydrogenation process technology and combined) in the system, mainly in the chemical process technology based, from raw material constraints, you can change the original hydrocarbon structure. Thus II base oils fewer impurities (aromatics content of less than 10%), high content of saturated hydrocarbons, thermal stability and oxidation resistance, low temperature and soot dispersion properties are better than I base oils.
Group III base oils are prepared with whole hydrogenation process, compared with Group II base oil, a high viscosity index base oil hydrogenation, also called unconventional base oils (UCBO). Group III base oil in the performance far more than Group I base oils and Group II base oils, especially those with a high viscosity index and low volatility. Some performance Class III oil with poly α- olefin (PAO) is comparable, its price is much cheaper than synthetic oil.
Group IV base oils are poly α- refers olefin (PAO) synthetic oils. Production methods commonly used paraffin decomposition method and ethylene polymerization. PAO according to the degree of polymerization can be divided into low degree, the degree of polymerization, high degree of polymerization, were used to modulate the different oil. Compared to such base oil and mineral oil, no S, P and metal, does not contain wax, so the pour point is very low, usually below -40 ℃, viscosity index is generally more than 140. But PAO boundary lubrication is poor. In addition, because of its own polarity is small, ability to dissolve polar additive is poor, and the rubber seal of a certain shrinkage, but these problems can be by adding a certain amount of esters to customer.
Other synthetic oils (synthetic hydrocarbons, esters, silicone oil, etc.) in addition to the class I ~ IV base oil, vegetable oil, base oil regeneration collectively V base oils.
The technical requirements of the 21st century lubricating base oils are: thermal oxidation stability, low volatility, high viscosity index, low sulfur / sulfur-free, low viscosity, and environment-friendly. The traditional "old three" process to produce Class I lube base oil lubricants can not meet this requirement in the future, hydrogenation production II or III base oils will become mainstream.
Our lubricant base oil standard established in 1983, to meet the needs of high-grade lubricants modulation, in 1995 the original standard was revised execution lube base oil classification methods and specifications standard QSHR 001-95, as shown in Table -2. This classification method and classification internationally has fundamentally different.

Table of base oil classification -2
Viscosity index VI
Annual Index

Viscosity Index

Viscosity Index

Viscosity Index

Viscosity Index

Universal base oil UHVI VHVI HVI MVI LVI
Special base oils Low freezing UHVI W VHVI W HVI W MVI W
The standard by viscosity index base oil into the low viscosity index (LVI), the viscosity index (MVI), a high viscosity index (HVI), a high viscosity index (VHVI), ultra-high viscosity index (UHVI) base oil 5 files. By using the range, the base oil into common base oils and special base oil. Special base oil is divided for multi-stage engine oil, hydraulic oil and hydraulic transmission cryogenic liquid products such as low pour base oil (suffix W) and suitable for turbine oils, extreme pressure industrial gear oil, refined products base oil (suffix S). Which HVI oils and VI> MVI oil 80 belong to the International Classification of Group I base oil; while VI <80 of MVI base oil and base oil did not join the class LVI; VHVI, UHVI according to the international classification of Class II and III base oil, but in terms of sulfur content and saturated hydrocarbons are not clearly defined.
Mineral oil is a base oil of high boiling point, high molecular weight hydrocarbons and non-hydrocarbon mixture is derived by a series of processing, mainly consisting of alkanes, cycloalkanes, aromatics, naphthene aromatics and oxygen-, nitrogen-containing sulfur compounds and resins, asphaltenes and other non-hydrocarbon compounds, virtually no olefins. Lubricating material on fractions, its hydrocarbon carbon number distribution of about C20 ~ C40; boiling range of about 350 ~ 535 ℃; relative molecular mass of 250 to 1000 or individual higher.
Hydrocarbons are the main component of the lubricating oil, lubricating oil viscosity hydrocarbon structure, viscosity-temperature properties, freezing point and other properties were significantly affected.
(A) the impact on the viscosity
Mineral base oil to hydrocarbon-based, hydrocarbon viscosity and its molecular structure, molecular size, number and type of ring-related.
The viscosity of the lubricating oil increases with the molecular weight of hydrocarbons; same number of carbon atoms in a variety of hydrocarbons, the minimum viscosity of alkanes, aromatics Small, cycloalkane maximum viscosity, and with the number of rings the proportion of the molecule increases; the number of rings in the same hydrocarbon viscosity increases with increasing side chain length.
(2) the impact on the viscosity-temperature properties
Viscosity index itself is a big difference between the hydrocarbons in the oil products contained hydrocarbons to n-alkanes highest viscosity index could reach 180 or more; isoparaffin viscosity index lower than the corresponding n-alkanes to some degree of branching increases and with decreased; followed by the alkyl side chains having a single ring, bicyclic and monocyclic cycloalkyl, bicyclic aromatic hydrocarbons; worst heavy aromatics, naphthenes and multi-ring naphthene - aromatic hydrocarbons ; for bicyclic and polycyclic hydrocarbons, with the number and viscosity index increasing the length of the side chains increases, and increases sharply with the number of rings; gum oxygen-containing polycyclic compound, the viscosity-temperature properties worse.
(3) on the freezing point of
Pour point of hydrocarbon descending order: n-alkanes> iso-paraffins> naphthenes> aromatics. N-alkanes highest freezing point, and with the increasing number of carbon atoms increases. Such as n-hexadecane freezing point of 18.16 ℃, n-octadecane was 36.7 ℃; isoparaffin pour point than the corresponding n-alkanes is low, and with the degree of branching increases rapidly declining; sidechain cyclic hydrocarbon side chain branching greater extent, pour point depressants are also more quickly.
As can be seen from the effect of molecular structure on some physical properties of the lubricant, in order from the hydrocarbon structure of the molecule to alter the performance of the lubricating oil is restricted, so that when changing the molecular structure of a performance improvement, while the other properties are often deteriorates, only the appropriate choice to get the performance of a relatively comprehensive lubricants.