Is Your Synthetic Oil Really Synthetic?

 Or is it just made from super high refined plain old oil?

Apparently the vast majority of so called synthetic oil is simply highly refined regular oil, called group 3, with a bunch of additives.

Mobil v Castrol 

Apparently this where the BBB stepped in and said Castrol could advertise its plain old oil as synthetic.

So all the other companies started doing the same.

A true synthetic oil apparently--- true synthetic oils must be made from PAO (polyalphaolefin) or diester base stocks, not refined crude. 

None of the links here will work. Mobil vs Castrol Lawsuit (1999):

In the late 1990s, Mobil sued Castrol over its Castrol Syntec oil, which used Group III base stock—a highly refined mineral oil—and was marketed as "full synthetic." Mobil argued this was false advertising, claiming true synthetic oils must be made from PAO (polyalphaolefin) or diester base stocks, not refined crude. 

The case was decided by the National Advertising Division (NAD) of the Council of Better Business Bureaus in 1999.  The ruling concluded that the term "synthetic" referred to performance properties, not the chemical origin or manufacturing process.  Therefore, Castrol was allowed to continue labeling its Syntec oil as synthetic, even though it was based on Group III mineral oil. 

This decision had a major industry impact:

• Most oil companies began reformulating their "synthetic" oils to use cost-effective Group III base stocks blended with additives. 

• Mobil 1 itself shifted to primarily using Group III unconventional base oils, despite its original formulation being a true synthetic. 

• The term "synthetic" became a marketing label based on performance, not chemistry, leading to widespread confusion among consumers. 

Today, most "full synthetic" oils sold in the U.S. are based on Group III, while true synthetic oils (using PAO or esters) are found in higher-end or specialty products like Amsoil, Royal Purple, or Motul 5100.