Synthetic Oil Groups

• There are three basic types of synthetic oil segregated into groups. Group I and group II are conventional oil. Groups III, IV and V oils are synthetic. Group III synthetic oil is considered a synthetic only in the U.S. It is the only group of synthetic oil that gets its base from crude oil, by the process of being hydrocracked and or hydroisomerized. According to Mike Allen from Popular Mechanics, group IV oils "consist of molecules that are synthesized from simpler chemical compounds." Group V oils are also synthesized from chemical compounds.
  
  

Common Types

• There are four common types of true synthetic base oils. One of the more common types is polyalphaolefins, or PAOs, and there is polyalkaline glycols referred to as PAGs. Two ester formulas are dibasic acid ester, or diester, and polyol ester, which are lass common. These four compounds make up the majority of synthetic oils in use today. PAO makes up group IV, while PAG and esters type oil make up group V. Group III uses crude as its base and is classified as synthetic not by how it's processed, but by its physical properties that perform near the same as PAOs.
  
  

Group Classifications Detailed

• The API classifies oils into groups that meet certain criteria. This criteria determines which group an oil will fall into. Group III oils are refined from crude and are considered synthetic for marketing purposes. According to a Machinery Lubrication publication, "the 1999 ruling of the National Advertising Division of the Better Business Bureau which allowed lubricants made with Group III oils to be labeled 'synthetic.'"
  
  Group III base stocks contain greater than or equal to 90 percent saturates and less than or equal to 0.03 percent sulfur and have viscosity index greater than or equal to 120.
  
  Group IV base stocks are polyalphaolefins (PAO).
  
  Group V base stocks include all other base stocks not included in groups I, II, III or IV.
  
  

Synthetic vs. True Synthetic

• True synthetic oils must be synthesized from chemical compounds. This process produces molecules of the same size and shape and can be engineered to perform in a wide range of operating conditions. Though group III is allowed to be labeled as synthetic, its base comes from crude oil. This is not to say that group III oils are inferior; they meet or exceed PAOs in some performance tests.
  
  

Synthetic Blends

• Synthetic blends are conventional oil with a small percentage of full synthetic added. Though the amounts are proprietary, it is most often about 10 percent synthetic. These oils are not among the group III, IV or V oils and are not considered synthetic.