Hitler ordered his scientists to come up with a petro alternative. I think it is fair to say he was responsible for its production.
US Military adopted its use. Later a military guy sold to the public as Amsoil.
Much of the oil sold now over-the-counter does NOT have the characteristics of the true synthetic oils like still used in jets or in race cars. Thus why I asked you what specific oil you are talking about.
Some petro-based Shell Rotella oils have higher heat durability then many oils sold as "pure synthetic."