What the Different Base Oil Groups Mean

The oil industry is vital to the success of several other industries—not to mention the economy. Between Group I, II, III, IV, and V base oils, each group has its defining characteristics. Continue reading to learn what the different base oil groups mean.

Group I

A Group I oil is defined as an oil with less than 90 percent of saturates and greater than .03 percent sulfur. Due to the lower amount of saturates, Group I oils are the most affordable to manufacture and purchase. However, as government rules and regulations have been modified in recent years, the oil industry is pivoting away from Group I oils.

Group II

Group II base oils are higher-grade and better-quality oils manufactured through hydrotreating. Group II base oils have greater than or equal to 90 percent saturates and less than or equal to .03 percent sulfur. Group II oils are very common base oils today, as they’re clearer, purer forms of Group I oils. However, similar to Group I oil, the viscosity index is greater than or equal to 80 but no more than 120.

Group III

As the demand for clearer and purer oil grows, Group III oils are commonly produced using hydrocracking, but they can also come from hydrotreating and hydroisomerization. Group III oils have the same sulfur and saturate percentages as Group II base oils, but Group III’s viscosity index is greater than 120. Much like Group II oils, Group III oils have become much more common throughout industries because they’re still affordable but better-quality.

Group IV

This group is different from the previous three because Group IV base oils are polyalphaolefin (PAO)––better known as synthetic. That said, they’re excellent in several applications, most notably for scenarios involving extreme temperatures. Since Group IV base oils are synthetic, they don’t have saturate or sulfur percentages. However, the viscosity index is at least 125 but equal or lesser than 200.

Group V

These base oils comprise all other oils—we know, very technical. Some of these oils may include silicone, phosphate ester, biolubes, and more. Group V oils are rarely used as base oils—they’re usually a part of a formula to create another base oil.

Now that you know what the different base oil groups mean, you can accurately define the different groups. Furthermore, you’ll be able to apply high-performance base oils to your particular need based on viscosity index, saturates, and sulfur percentages.