Base oil is the name given to lubrication grade oils initially produced from refining crude oil  (mineral Base Oil) or through chemical synthesis (synthetic base oil). It is the oil with a boiling point that range between 288  ̊C and 566  ̊C. It consists of hydrocarbons with 18 to 40 carbon atoms. Base Oils typically make up 70% to 99% of a lubricant’s formulation and are refined by various methods, mostly from crude oil. The type, source and refining method that are used determine the properties of the oil.

The traditional method of producing base oils is to feed straight-run fuel oil into a Vacuum Distillation column, the output of which can either go into fuels processing or be fed into a solvent extraction plant. The fluid is further treated to remove unwanted properties such as wax, sulfur, and aromatics.
Unlike most other oil and chemical products, there is no industry standard for base oils. Most refineries manufacture different quality base oils. In automotive usage, viscosity index, pourpoint, oxidation stability and volatility are important, but there are other important criteria for measuring base oils in industrial applications for example.

 

Lab Tests on Base Oil to Check Quality

Various tests are conducted on Base oil to assessthe properties of base oil materials. The following tests are usually conducted to evaluate different properties of them.

Test ASTM
Acid Number D664
Aniline Point D611
Color D1500, D6045
Density D1298, D4052
Flash Point D92, D93
Pour Point D97, D5950, D5949, D6749
Sulfur D2622, D4294, D5453
Viscosity, Kinematic D445, D2270, D7042
Volatility D6417
Water D6304, D1401

Base Oil SN 150
Base Oil SN150 
Characteristic Test Method Value
Appearance Visual C , B
Color ASTM D-1500 Max 1
Viscosity @ 100 oC, CSt ASTM D-445 4.7-5.7
Viscosity Index; Min ASTM D-2270 Min 90
Flash Point, (Min) oC ASTM D-92 Min 200
Pour Point, (Max) oC ASTM D-97 Max 6

Base Oil SN500 (High VI)
Base Oil SN500 (High VI)
Characteristic Test Method Value
Appearance Visual C & B
Color ASTM D-1500 Max 1
Viscosity @ 100 oC, CSt ASTM D-445 Min 10.5-11.2
Viscosity Index; Min ASTM D-2270 Min 90
Flash Point, (Min) oC ASTM D-92 Min 245
Pour Point, (Max) oC ASTM D-97 Max 6

Base Oil SN500 (Low VI)
Base Oil SN500 (Low VI)
Characteristic Test Method Value
Appearance Visual C & B
Color ASTM D-1500 Max 2
Viscosity @ 100 oC, CSt ASTM D-445 Min 10.8
Viscosity Index; Min ASTM D-2270 Min 87
Flash Point, (Min) oC ASTM D-92 Min 235
Pour Point, (Max) oC ASTM D-97 Max 3

Base Oil SN600 (High VI)
Base Oil SN600 (High VI)
Characteristic Test Method Value
Appearance Visual C & B
Color ASTM D-1500 Max 1.5
Viscosity @ 100 oC, CSt ASTM D-445 Min 23
Viscosity Index; Min ASTM D-2270 Min 90
Flash Point, (Min) oC ASTM D-92 Min 246
Pour Point, (Max) oC ASTM D-97 Max 6

Base Oil SN600 (Low VI)
Base Oil SN600 (Low VI)
Characteristic Test Method Value
Appearance Visual C & B
Color ASTM D-1500 Max 3
Viscosity @ 100 oC, CSt ASTM D-445 Min 12.6
Viscosity Index; Min ASTM D-2270 Min 80
Flash Point, (Min) oC ASTM D-92 Min 235
Pour Point, (Max) oC ASTM D-97 Max 3

Packing

  • Bulk
  • Flexi Tank
  • Drum

Base Oil Groups

The American Petroleum Institute (API) has categorized base oils into five categories. The first three groups are refined from petroleum crude oil. Group IV base oils are full synthesis (poly-alpha olefin) oils. Group V is for all other base oils not included in Groups I through IV. Before all the additives are added to the mixture, lubricant oils begin as one or more of these five API groups.

Group I – These oils are usually processed with solvents and they have a good degree of solvency, but they are most vulnerable to oxidation and thermal degradation compared to oils processed in different manner. The oils of Group I are used in almost all applications in the automotive and industrial field and are important for the formulation of lubricating greases. Group I base stocks contain less than 90 percent saturates and/or greater than 0.03 percent sulfur and have viscosity index greater than or equal to 80 and less than 120.

Group II base oils are characterized as being in excess of 90% soaks, under 0.03% sulfur and with a consistency index of 80 to 120. They are regularly made by hydrocracking, which is a more intricate process than what is utilized for Group I base oils They have high saturation levels, and good performance in terms of thermal and oxidation stability. These oils are used in a large range of automotive and industrial applications.

Group III base oils are subjected to the highest level of mineral oil refining of the base oil groups. Although they are not chemically engineered, they offer good performance in a wide range of attributes as well as good molecular uniformity and stability. They are commonly mixed with additives and marketed as synthetic or semi-synthetic products. Group III base oils have become more common in America in the last decade.

Group IV base oils are chemically engineered synthetic base stocks. Polyalphaolefins (PAO’s) are a common example of a synthetic base stock. Synthetics, when combined with additives, offer excellent performance over a wide range of lubricating properties. They have very stable chemical compositions and highly uniform molecular chains. Group IV base oils are becoming more common in synthetic and synthetic-blend products for automotive and industrial applications.

Group V base oils are used primarily in the creation of oil additives. Esters and polyolesters are both common Group V base oils used in the formulation of oil additives. Group V oils are generally not used as base oils themselves, but add beneficial properties to other base oils. Some examples of Group V Base Oils are: Alkylated Naphthalene, Esters, Poly-alkylene glycols, Silcones, Polybutenes.

Base Oil Physical Properties:

Base oils are described by four physical properties that dictate how they will perform in service:

  1. Pour point. The lowest temperature at which a sample of oil can be poured determines the pour point.
  2.  Viscosity. An oil’s resistance to flow defines the viscosity.
  3.  Viscosity index. As an oil’s temperature changes, so does its viscosity, defining its viscosity index. A high viscosity index oil, for example, changes viscosity less with temperature than a low one. High Viscosity index base oils have lower volatility and are designed to operate at low as well as high temperatures
  4. Purity. Constituents of many lubricants such as sulfur, nitrogen and polycyclic aromatic compounds must be held within strict limits.

 

Base Oil Application

The main use for base oils is in the manufacture of lubricants, of which there are many thousands of types. The best-known are automotive lubricants, but there are many more applications in which lubricants are used, some of which are highly specialised. One litre of lubricants is composed of anywhere between 50% and 90% base oil, the rest being made up of additives.

Group Type Sulfur, Wt% Saturates Viscosity Index Process Comments
I Mineral > 0.03  and / or < 90 80 – 119 Solvent refined Too much Sulfur for current specs
II Mineral ≤ 0.03  and ≥ 90 80 – 119 Hydro-Processed Comparable Purity Increasing Viscosity Index
III Mineral ≤ 0.03  and ≥ 90 > 120 Hydro-Cracked Comparable Purity Increasing Viscosity Index
IV Synthetic All Polyalpha Olefins (PAO’s) All Polyalpha Olefins (PAO’s) All Polyalpha Olefins (PAO’s) Chemical reaction Synthetics
V Synthetic All other Synthetics All other Synthetics All other Synthetics All other Synthetics Small Volumes
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