The term “base oil” refers to lubrication-grade oils that are initially created by refining crude oil (mineral base oil) or chemical synthesis (synthetic base oil). According to standard definitions, base oil is a type of oil having a boiling point between 550 and 1050 F and a composition of hydrocarbons with 18 to 40 carbon atoms. Depending on the molecules’ chemistry, this oil may be paraffinic or napthenic in composition.
Almost all of the lubricants used in plants today began as simple basic oils. Base oils are divided into five categories by the American Petroleum Institute (API) (API 1509, Appendix E). Out of petroleum crude oil, the first three types are refined. Group IV base oils are polyalphaolefin (fully synthetic) oils. All additional basic oils that are not a part of Groups I through IV fall under Group V. Lubricating oils are initially classified as one or more of these five API categories before any additives are added to the combination.
Typical Properties of Each Base Oil Group
GroupⅠ | GroupⅡ | GroupⅢ | Ultra-S 4,6,8 | GroupⅣ | |
---|---|---|---|---|---|
Saturates, % | 65~85 | 93~99+ | 95~99+ | 99+ | 99+ |
Aromatics, % | 15~35 | <1~7 | <1~5 | <1 | <1 |
Sulfur, ppm | 300~3000 | 5~300 | 0~30 | <1 | n/a |
Viscosity @ 100℃, cSt | 4~32 | 4~30 | 4~8 | 4.0~7.6 | 4~70 |
Viscosity Index(VI) | 95~105 | 95~118 | 123~150 | 120~135 | 125~150 |
Pour point, ℃ | -15 | -15 | -15 | -22.5 ~ -15 | -45 |
Base stocks are classified inot various grades including Neutral, Solvent Neutral, Bright Stocks, The most common names are for group I (SN: Solvent Neutral), for group II (N: Neutrals) and group III grade names refer to the viscosity (4cst, 6cst, 8cst …).
Group I - Baseoil Grades - Technical Specifications
Characteristic
|
Units
|
SN-150
|
SN-500
|
Bright Stock
|
Test Method
|
---|---|---|---|---|---|
Kinematic viscosity at 100°C |
cSt
|
4.4 – 5.6
|
9.7 – 12.0
|
min. 28
|
ASTM D-445
|
Kinematic viscosity at 40°C |
cSt
|
28 – 32
|
90 – 105
|
–
|
ASTM D-445
|
Viscosity index (VI) |
–
|
95 – 100
|
95 – 100
|
min. 95
|
ASTM D-2270
|
Flash Point |
°C
|
min. 195
|
min. 210
|
min. 276
|
ASTM D-92
|
Sulphur Content |
%Wt
|
0.15 – 0.60
|
0.15 – 0.60
|
0.15 – 0.60
|
ASTM D-2622
|
Pour Point |
°C
|
max. -6
|
max. -6
|
max. -9
|
ASTM D-97
|
Density @ 15°C |
Kg/L
|
0.870 – 0.890
|
0.885 – 0.895
|
0.900 – 0.910
|
ASTM D-1298
|
Color |
–
|
max. 2
|
max. 2
|
max. 2
|
ASTM D-1500
|
TAN |
mg KOH/g
|
max. 0.05
|
max. 0.05
|
max. 0.05
|
ASTM D-664
|
Carbon Residue Content |
%Wt
|
0.04
|
0.12
|
0.21
|
ASTM D-189
|
Group II - Baseoil Grades - Technical Specifications
Characteristic
|
Units
|
N-150
|
N-500
|
Test Method
|
---|---|---|---|---|
Kinematic viscosity at 100°C |
cSt
|
5.0-5.6
|
10.0-12.0
|
ASTM D-445
|
Kinematic viscosity at 40°C |
cSt
|
28-32
|
95-107
|
ASTM D-445
|
Viscosity index (VI) |
–
|
95-110
|
95-110
|
ASTM D-2270
|
Flash Point |
°C
|
min. 210
|
min. 230
|
ASTM D-92
|
Sulphur Content |
%Wt
|
max. 0.012
|
max. 0.012
|
ASTM D-2622
|
Pour Point |
°C
|
max. -12
|
max. -12
|
ASTM D-97
|
Group III - Baseoil Grades - Technical Specifications
Characteristic
|
Units
|
4cSt
|
6cSt
|
8cSt
|
Test Method
|
---|---|---|---|---|---|
Kinematic viscosity at 100°C |
cSt
|
4.1 – 4.4
|
5.7 – 6.5
|
7.6 – 8.2
|
ASTM D-445
|
Kinematic viscosity at 40°C |
cSt
|
19.0 – 20.0
|
32.0 – 37.0
|
43.8 – 50.1
|
ASTM D-445
|
Viscosity index (VI) |
–
|
min. 120
|
min. 120
|
min. 120
|
ASTM D-2270
|
Flash Point |
°C
|
min. 220
|
min. 220
|
min. 220
|
ASTM D-92
|
Sulphur Content |
%Wt
|
0.001
|
0.001
|
0.001
|
ASTM D-2622
|
Pour Point |
°C
|
max. -12
|
max. -12
|
max. -12
|
ASTM D-97
|
API BASE OIL CATEGORIES | ||||
---|---|---|---|---|
Base Oil Category | Sulfur (%) | Saturates (%) | Viscosity Index | |
Group I (solvent refined) | >0.03 | and/or | <90 | 80 to 120 |
Group II (hydrotreated) | <0.03 | and | >90 | 80 to 120 |
Group III (hydrocracked) | <0.03 | and | >90 | >120 |
Group IV | PAO Synthetic Lubricants | |||
Group V | All other base oils not included in Groups I, II, III or IV |
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