Synthetic is superior. Problem is in the States, there are ZERO mandates or any government regs or federal anything that states when you put synthetic on the bottle or call it a full synthetic, it's actually 100% synthetic oil inside the jug. Talking about a full 100% synthetic base stock and add pack. Europe is totally different. If it says synthetic over there, you get synthetic IN the bottle.
slomo
In fact there is a lot of confusion, but I wouldn't say that...
There are only two oil bases: mineral and synthetic
The mineral is 100% petroleum-derived, with additives
Semi-synthetic is a mix of mineral + synthetic (created in laboratory), with additives
The synthetic is 100% synthetic (created in the laboratory), with additives
When manufacturers place SAE and API (or ISO, ILSAC) stamps, they do so under the authorization of such institutions and pay for it.
What represents one oil being superior to another is exactly the API qualification (SJ, SL, SN...), which is modernity or superiority...
The fact that it is synthetic does not qualify the oil as superior. See for example:
1- Mineral SAE 5W30 API SN (
https://lucasoil.com/products/lucas-motor-oil/conventional/lucas-petroleum-motor-oils)
2 - Synthetic SAE 5W30 API SN (
https://www.mobil.com/en/lubricants/for-personal-vehicles/our-products/products/mobil-1-5w-30/)
Note that both have the same SN classification, but nr 1 is mineral and nr 2 is synthetic, therefore equal in meeting the same standardized efficiency tests.
See that both manufacturers say theirs is superior, the maximum, the best, the top... believe what you want, but the American Petroleun Institute (API) rated them equal.