Thank you for the link. Here are the Noack x CCS values -- the lower the product, the higher the base-oil quality. Mobil 1 has by far the highest-quality base oil and Castrol has the lowest-quality base oil as usual. However, Castrol 0W-20's base oil is still fairly decent -- other Castrol viscosity grades (except Euro grades such as 0W-40) tend to be near the bottom in base-oil quality, using the cheapest Group III base stocks. Super Tech HM 0W-20 has surprisingly a GTL or a Group III+++ base oil.
Code
Noack x CCS rating
(a lower value indicates higher API base-stock groups
and/or a higher base-oil (not finished-oil) viscosity index (VI))
1. M1 HM 0W-20: 51,100 (GTL + PAO + AN)
2. ST HM 0W-20: 56,500 (GTL or Group III+++)
3. PP HM 0W-20: 56,800 (GTL or Group III+++)
4. Valvoline FS HM 0W-20: 61,500 (Group III+)
5. Castrol 0W-20: 62,100 (Group III+)