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Well, once upon a time Microsoft advertised "32-bit mouse" for 32-bit Windows-95. Not better nor worse... but still border a fraud.
There are some interesting specifications and data for different oils on that page.
Basically, the Amsoil XL oils are API approved, which is a bunch of marketing hype. Because of the lower levels of phosphorous and such, they don't recommend them as extended drain oils. They simply offer them to people who want a warm and fuzzy by staying within manufacturers recommendations. Here is a better explanation:
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