It does not matter if its 100% synthetic, only thing matters is film strength at normal and high temps - how well it protects engine. There are many conventional oils that protect better than synthetic oils.the problem is oil co.went to court to get approval to sell mineral based oil w/ additives as synthetic it says "full synthetic "on can but is mineral based. It has to say 100% synthetic to be non dinosaur base oil.Everything you say here is correct but can get you punched in face by know it all at autozone.(how dare you imply they have been putting not synthetic full synthetic oil in their car)
For example Roual Purple is 100% synthetic and is mediocre when it comes to engine protection and is outshined by many conventional oils.
Pure synthetic or not - does not make any difference.
Best oil for the money - Quaker state - baced on independent testing.
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