Base Oil
All lubricants consist of a base oil. Normally, lubricants consist of 90% base oil and 10% additives. The American Petroleum Institute (API) has categorized base oils into five groups (I, II, III, IV, V) which are specified by the saturate level, sulfur level, and viscosity index.
Saturate Level
Saturates are a type of molecule commonly found in base oil. They are naturally present in base oil but during the refining process higher levels of saturates are obtained. If the level of saturates is higher, the molecular bond of the oil is stronger. This will increase the resistance to breakdown and oxidation or the loss of viscosity.
Sulfur Level
Sulfur is a natural inorganic element occurring in crude oil. Because it reacts with oxygen it can be harmful to the performance of oil. It can also be damaging to exhaust after treatment devices. Besides these negative aspects of sulfur there are also some positive aspects. Sulfur can be an effective antioxidant which improves the oxidative stability. When the content of sulfur is lower, the purity is better which decreases the probability of corrosion and oxidation.
Viscosity Level
The Viscosity Index refers to the changes in viscosity compared to the temperature of the oil. The viscosity is measured at 40 °C and 100 °C. When the viscosity index is high, the changes are smaller with differences in temperature. All oils increase in viscosity when the temperature decreases and decrease in viscosity when temperatures increase.
Base oils are used to manufacture products including lubricating greases, motor oil and metal processing fluids. Different products require different compositions and properties in the oil.
Base Oil Categories
Base Oil | Sulfur (%) | Saturates (%) | Viscosity Index | |
|---|---|---|---|---|
Group I | >0.03 | <90 | 80 to 120 | |
Group II | <0.03 | >90 | 80 to 120 | |
Group III | <0.03 | >90 | >120 | |
Group IV | PAO Synthetic Lubricants | PAO Synthetic Lubricants | PAO Synthetic Lubricants | |
Group V | PAO Synthetic Lubricants | PAO Synthetic Lubricants | PAO Synthetic Lubricants |
Group I
Group I oils are solvent-refined, which is a simpler refining process, making them the least refined and therefore also the cheapest base oils available. Solvent-refined oils consist commonly of a mix of different hydrocarbon molecules which cannot be distinguished in the refining process. This results in an oil with irregular molecules causing increased friction within the oil. Group I oils are therefore used most often in less demanding applications. Group I base oils are classified as less than 90 percent saturates, greater than 0.03 percent sulfur and with a viscosity range of 80 to 120. The temperature range for these oils is from 32 to 150 degrees F. Group I base oils are solvent-refined, which is a simpler refining process which is why this is why they are the cheapest base oils on the market.
Group II
Group II base oils undergo hydro cracking which is a more complicated process than the process for Group I oils. Hydro cracking is a process that breaks down large hydrocarbon molecules into smaller ones. The hydrocarbon molecules of these oils are saturated, giving them better anti oxidation properties. Group II oils are priced closely to Group I oils. base oils are defined as being more than 90 percent saturates, less than 0.03 percent sulfur and with a viscosity index of 80 to 120. They are often manufactured by hydrocracking, which is a more complex process than what is used for Group I base oils. Since all the hydrocarbon molecules of these oils are saturated,
Group II base oils have better antioxidation properties. They also have a clearer color and cost more in comparison to Group I base oils. Still, Group II base oils are becoming very common on the market today and are priced very close to Group I oils.
Group III
Group III oils undergo an even longer process than Group II oils. The process, called severe hydro cracking, is also more intense. More pressure and heat is applied during the refinery process. This results in a purer base oil with a higher quality. Even though Group III oils are derived from crude oil, they are sometimes described as synthesized hydrocarbons. base oils are greater than 90 percent saturates, less than 0.03 percent sulfur and have a viscosity index above 120. These oils are refined even more than Group II base oils and generally are severely hydro cracked (higher pressure and heat). This longer process is designed to achieve a purer base oil.
Although made from crude oil, Group III base oils are sometimes described as synthesized hydrocarbons. Like Group II base oils, these oils are also becoming more prevalent.
Group IV
Group IV base oils are Polyalphaolefins (PAOs). These synthetic base oils are made through a process called synthesizing. They have a much broader temperature range and are great for use in extreme cold conditions and high heat applications.
Group V
Group V base oils are classified as all other base oils, including silicone, phosphate, ester, polyalkylene glycol, polyolester, biolubes, etc. These base oils are at times mixed with other base stocks to enhance the oil’s properties. An example would be a PAO-based compressor oil that is mixed with a polyolester.
Esters are common Group V base oils used in different lubricant formulations to improve the properties of the existing base oil. Ester oils can take more abuse at higher temperatures and will provide superior detergency compared to a PAO synthetic base oil, which in turn increases the hours of use.
Properties of each Base Oil Group
| Group I | Group II | Group III | Group IV | Group V | |
|---|---|---|---|---|---|
| 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 |
For more information about our available grades and specifications, please contact us directly by email at Info@rhineme.com.