HTO-06 was developed by Honda because they had found that TEOST was not a good test because it only tested new oil. When you introduce combustion byproducts into the oil, many oils failed miserably at preventing deposits. Honda R&D at that time found only Mobil 1 passed it, by a large margin, while others did not.
This is why I stopped paying attention to Amsoil's TEOST marketing material around that time. Joe 90 Guy also said it's a useless test. Nice bench test for marketing I suppose. But real world validity it falls short.
The GM turbo test is now the standard I believe.
Shell makes great oils but if you didn't know anything about motor oil you'd think Platinum is just made of Gas to Liquid base oils lol.
One of the members received an email from SOPUS when asking about QSUD vs Platinum in which they stated the couldn't guarantee QSUD was 100% GTL Base. It sure sounded like they at least wanted people to think Platinum used 100% GTL Base.