Here is my rant on "synthetic" oils.
The term synthetic is a worthless and very abused word in the oil industry. The truth is all oils are made from the remains of vegetation from the Jurassic period. It will be made from crude oil or natural gas or maybe even coal dust.
If we are lucky we will get a highly refined lubricant in a bottle marked "synthetic". Most synthetics are made from highly refined crude oil.
But, there is no specification or regulation saying what may be called synthetic.
Legally an oil company could bottle some "Head and Shoulders" shampoo and sell it as synthetic oil.
By the way "Head and Shoulders" shampoo will pass a Timkin oil film test with excellent results.
It would be a lot more useful if oil was sold according to the class of lubricant.
Class 1 has minimal refining and contains impurities that reduce it's lubricating qualities.
Class 2 has more refining
Class 3 is better yet
Class 4 and 5 are what we would generally refer to as "synthetics" as they are highly refined
Class 4 are usually PAO bases and Class 5 are usually ester bases.
But oils are not generally advertised this way. Calling the oil company may get the answer or they may just say it is proprietary information.
Royal Purple and MPT said their "synthetics" are a blend of group 4 and group 5 oils.
Mobil 1 would not say. I would guess they're using some group 3 oils in their mixtures.
https://www.machinerylubrication.com/Read/29113/base-oil-groups