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 ranges between 288 ̊C and 566 ̊C. It consists of hydrocarbons with 18 to 40 carbon atoms. Base Oils typically makeup 70% to 99% of a lubricant’s formulation and are refined by various methods, mostly from crude oil. The type, source, and refining methods 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 assess the properties of base oil materials. The following tests are usually conducted to evaluate different properties.
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
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.
| 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) | ||
| 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) | ||
| 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) | ||
| 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) | ||
| 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
- FlexiTank
- 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. poly alpha olefins (PAO’s) are a common example of 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 polyesters 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:
- Pour point. The lowest temperature at which a sample of oil can be poured determines the pour point.
- Viscosity. An oil’s resistance to flow defines the viscosity.
- Viscosity index. As an oil’s temperature changes, so do 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
- 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 specialized. One liter of lubricants is composed of anywhere between 50% and 90% base oil, the rest is 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 |
