The American Petroleum Institute (API) classifies base oils into five main categories, ranging from traditional mineral oils (Group I) to a variety of synthetic and specialty oils (Groups IV and V). Each group has its own characteristics that determine their application, production process and behavior in various conditions. Understanding these categories is key to answering the question of mixing synthetic oils.
In this article, we will look at the main categories of base oils according to the API classification, their characteristics and features, answer frequently asked questions and try to figure out in which cases and for what purposes oil mixing can be used. This will help us understand whether and how it is safe to mix different types of synthetic oils, as well as what the consequences of such mixing may be for industrial equipment and automotive engines.
API base oil categories
These categories are determined based on the production process, chemical composition and application of oils in various conditions. Here is a brief description of each group:
- Group I: These oils contain less than 90% saturated hydrocarbons and more than 0.03% sulfur. Their viscosity index ranges from 80 to 120. These are the most affordable oils on the market.
- Group II: Oils of this group contain more than 90% saturated hydrocarbons and less than 0.03% sulfur. They have better antioxidant properties and a cleaner color compared to Group I oils.
- Group III: Oils with a saturated hydrocarbon content of more than 90% and less than 0.03% sulfur, the viscosity index of which is higher than 120. These oils undergo more thorough purification and are sometimes described as synthesized hydrocarbons.
- Group IV: Polyalphaolefins (PAO), fully synthetic oils. They are suitable for use in extremely cold conditions and at high temperatures.
- Group V: Includes all other base oils not included in the previous groups, such as silicone, phosphate ester, polyalkylene glycol (PAG) and others.
| Group | Description | Viscosity index | Features |
|---|---|---|---|
| Group I | Less than 90% saturated hydrocarbons, more than 0.03% sulfur | 80-120 | The most available oils |
| Group II | More than 90% saturated hydrocarbons, less than 0.03% sulfur | 80-120 | Best antioxidant properties |
| Group III | More than 90% saturated, less than 0.03% sulfur | > 120 | Synthesized hydrocarbons |
| Group IV | Polyalphaolefins (PAO) | > 120 | Suitable for extreme temperatures |
| Group V | All other base oils | Varies | Wide range of applications |
What is oil mixing and why may it be required?
Oil mixing is a process in which two or more different types of oils are combined in one system. This can be done either intentionally to achieve certain oil properties, or accidentally, for example, when adding oil to an automobile engine or for urgent start-up of industrial equipment.
The reasons why oil mixing may be required include:
- The need to top up the oil: In automotive components and industrial equipment, it is sometimes necessary to top up the oil. If the exact same oil is not available, there may be a situation where you have to use a different type or brand of oil.
- Achieving certain characteristics: In some cases, oil mixing can be used to obtain desired properties such as improved viscosity, temperature stability, or chemical resistance. This is especially true in industrial environments, where the requirements for oils can be very specific.
- Saving resources: In some situations, mixing oils can be a cost-effective solution that allows you to use leftover oils instead of recycling them.
- Experimental and research purposes: In scientific research, oil mixing can be used to study the effect of different chemical compositions on the properties of oils and their behavior under different conditions.
What are the risks associated with mixing different types of oils?
Mixing oils of different types or brands can entail a number of risks and potential problems, especially if this is done without a proper understanding of their chemical compatibility. Here are the main risks associated with such mixing:
- Change in viscosity:Mixing oils with different viscosities can lead to unexpected changes in the overall viscosity of the mixture. This may affect the ability of the oil to provide adequate lubrication, especially in critical equipment operating conditions.
- Chemical incompatibility: Different oils contain different additives and base oils that can react with each other. This can lead to precipitation, deterioration of antioxidant and anti-corrosion properties, as well as a decrease in the effectiveness of additives.
- Deposit formation: Some oil combinations can lead to the formation of sludge or other deposits, which clogs the filters and channels of the lubrication system, impairing oil circulation.
- Reduced protective properties: Mixing can reduce the ability of the oil to protect against wear, corrosion and overheating, which is especially critical for engines and industrial equipment.
- Deterioration of temperature properties: Improper mixing can lead to changes in the thermal conductivity and temperature range of the oil, which affects the cooling and operation of the equipment at different temperatures.
The possibility of mixing synthetic base oils
Mixing of synthetic base oils can be performed, but with certain reservations and precautions. It is important to understand that not all synthetic oils are compatible with each other, and their mixing should be based on an understanding of their chemical composition and properties.
What base oils can be mixed:
- Mixing within the same group: Synthetic oils within the same API classification group (for example, all Group IV oils are polyalphaolefins) are most often compatible with each other.
- Mixing oils with similar additives: If the oils contain similar additives, the probability of their successful mixing is higher.
Which base oils are better not to mix:
- Different groups with different chemical properties: For example, mixing oils of Group IV (PAO) and Group V (esters, esters) can be problematic due to differences in their chemical composition.
- Oils with different types of additives:Various additives can interact with each other, causing deterioration of the properties of the oil.
Mixing ratio:
- There are no strict rules regarding mixing proportions, but it is recommended to minimize the amount of mixed oils. For example, when topping up, use no more than 10-20% of other oil from the total volume.
Mixing of synthetic and mineral oils
Mixing synthetic and mineral oils is technically possible, as many synthetic oils are compatible with mineral oils. However, there are several important points to consider:
- Deterioration of the properties of synthetic oil: Mixing with mineral oil can lead to the loss of some of the advantages of synthetic oil, such as improved thermal stability and lubricating properties.
- Effect on viscosity and stability: Mixing can change viscosity and thermal stabilitythe oil content, which may affect its effectiveness.
- Manufacturer's recommendations: The recommendations of the equipment manufacturer should always be taken into account. Some manufacturers may not recommend mixing synthetic and mineral oils for their equipment.
In conclusion, mixing synthetic oils is possible, but requires a careful approach and understanding of the properties and compatibility of oils. Mixing of synthetic and mineral oils is also possible, but may lead to deterioration of some properties of synthetic oil.
Output
Mixing oils is a complex process that can have both positive and negative consequences. It is important to take into account the chemical compatibility of oils, their viscosity and the types of additives. Although mixing can be useful in some cases to achieve certain properties, it can also lead to deterioration of the oil characteristics and lead to problems with the equipment. Innovations and research in this area are aimed at improving the compatibility and stability of oils, which can facilitate the mixing process in the future. However, it is always recommended to be careful!
For more information about mixing oils, you can contact our technical specialists.