Mineral base oils
There are 5 types of base oils used for the formulation of lubricants. The first 3 groups are called Mineral Oils.
Mineral oils come from the crude oil extraction, oil molecules are grouped by size and type in a distillation tower by means of atmospheric distillation and vacuum. The waxy residue with low sulfur content obtained at 400ºC is the fraction from which the Group I, II and III base oils are obtained.
One of the main differences between mineral oils and synthetic oils is the content of impurities that we can find in them. According to the API classification for base oils, the main impurities are mainly defined by the amount of sulfur and the presence of saturated compounds.
| API Categories for Base Oils | ||||
|---|---|---|---|---|
| Base Oil Category | Sulfur (%) | Saturates (%) | Viscosity Index | |
| GROUP I | >0.03 | and/or | <90 | 80 to 120 |
| GROUP II | <0.03 | and | >90 | 80 to 120 |
| GROUP III | <0.03 | and | >90 | >120 |
| GROUP IV | Synthetic Lubricant PAO type | |||
| GROUP V | Rest of base oils not included in Groups I, II, III or IV | |||
The main characteristics of mineral base oils are shown below:
GROUP I
Production process: Refined solvent
Advantages: Good solubility, low cost, seal compatibility
Disadvantages: Vulnerable to oxidation and thermal degradation, high volatility, low viscosity index
Applications: Engine oils, marine engine oils, gears, hydraulics, transformer oils
GROUP II
Production process: hydrotreated and catalytic dewaxing
Advantages: Good thermal and oxidation stability, hydrolytic stability, good low temperature behavior, low cost
Disadvantages: Additives solubility lower than group I
Applications: Engine oils, Automatic Transmission Fluids, Manual Transmission Fluids, Compressors, Turbines, Hydraulics
GROUP III
Production process: hydrocracking and advanced catalytic dewaxing
Advantages: High viscosity index and very good thermal and oxidation stability
Disadvantages: Additives solubility lower than group I and II
Applications: Premium engine oils, premium Automatic Transmission Fluids, premium Manual Transmission Fluids