Ten Facts That Nobody Told You About Base Oils

API Base Oil Groups

At the beginning of 1990 in the early 1990s, the American Petroleum Institute implemented a system to describe various bases of oil. This led to the development and introduction of group numbers for base oils

Base oils of Group I are the older, traditional base oils produced by the process of solvent refining to remove weaker chemical structures or harmful actors (ring structures, or structures that have double bonds) from crude oil. Refining with solvents was the principal technique employed in refineries constructed between 1940 and the year 1980.

Group 1

Group 1 – base oils generally vary from amber to golden brown because of the sulfur, nitrogen, and ring structures left inside the oil. They generally contain a viscosity index (VI) between 90 and 100. The base oils at the upper range are usually described as being a high-viscosity ratio (HVI).

This is related to how the viscosity changes as temperature increases, i.e., how it becomes thinner at higher temperatures and increases at lower temperatures. The Group I base oils is the most popular industrial oil type however, more and more Group II base oils are being utilized.

Group 2

Base oils of Group 2 are produced by the process of hydrotreating to replace the solvent-refining method that was previously used. The use of hydrogen gas helps eliminate undesirable elements from crude oil. It results in a clean and colorless base oil, with the least amount of nitrogen, sulfur, or rings.

The VI typically is over 100. In recent times the price has gotten quite like group I oil base products. Base oils from Group 2 are still considered mineral oils. They are used extensively in formulations for automotive engine oils.

Group 2 “Plus” is the name used for Group II base oils that have the slightest increase in VI, which is approximately 115. However, this isn’t an official term recognized according to the API.

Group 3

The Group 3 base oils are made by hydrogen gas to remove the crude oil, however this time, the process is more intense and operates at greater pressures and temperatures than the process used for Group 2 base oils. The final base oil is colorless and clear but is also a bit more viscous higher than 120. Additionally, it’s more resistant to the oxidation process than oils in Group 1 oils.

The price for group 3 base oils is more than the cost of Group 1 or 2. Base oils from Group 3 are considered to be mineral oils by a large number of experts due to their direct sourcing from refining crude oil. They are however considered bases that are synthetic by some individuals for marketing reasons due to the notion that the more harsh hydrogen process has resulted in new chemical structures for oil which were not previously present before the process. The process is believed that it has created (created) the new hydrocarbon structure. Check out the section on base oils that are synthetic in this book.

Group 1-2 and III base oils are essentially a reflection of the advancements in refinery technology over the last 70 to 80 years.

Group 4

Base oils of Group 4 include polyalphaolefin (PAO) base oils that are synthetic that have been in existence for over 50 years. They are chemical compounds that have been created in a chemical facility instead of being produced through distillation and refining crude oil (as the earlier groupings were).

PAOs are part of that category called synthetic hydrocarbons (SHCs). These oils have a 4 over 120 and are considerably priced higher than the base oils of Group III because of the extent of processing required to make them.

Group 5

The base oils of Group 5 comprise all base oils that aren’t included in Groups 1, 2-3, or 4. Thus, naphthenic base oils, as well as synthetic esters of various kinds, polyalkylene glycols (PAGs), and the phosphate esters as well as others, belong to this category.

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