quote:... isn't that the bare minimum one should expect today from an engine oil? Isn't that what the API starburst logo means?"
API is only a part of the big picture.
I can (partially) agree with you! But, if you’re really skeptic about Amsoil's quality because of not having API donut as (bare) minimum - do not use it! There is a lot other good synthetic (or even petroleum) products which do not guarantee you 7500, 25000 or 35000 miles drain period, however. Even Wal-Mart oils have the donut! So, choice is up to you.
Not mentioning to customers that they can extend drain periods with synthetics, maybe, is more honest approach? Perhaps Castrol's approach with fooling customers and having the donut is more appropriate? Being a huge company they allowed themselves to do what they want. Money does everything! Who cares about quality and customers?