I've lost track of which threads are what, so I'm asking here:
Gokhan, Why do you suppose that HPL's SAE 20 has noticeable VII in it? Related: Why do you suppose their 10W20 has essentially none?
Those things are what your spreadsheet claims, anyway.
Obviously for a monograde oil, A_Harman index ~ 1 and VII = (1−A_Harman index) ∕ 2 ~ 0.
HPL PCMO 20W-50 has VII ~ −3%, which is also obviously wrong.
HPL PCMO 10W-20 is probably also a SAE 20 monograde.
There are two possible explanations:
1. Specs of HPL oils significantly vary from batch to batch, and they used different batches to test for KV and HTHS. This would explain why some HPL monogrades have VII ~ 0 as expected, while others don't make sense. You need to use the same batch for KV and HTHS for the calculation to work.
2. ASTM D341 viscosity extrapolation fails for some of the base oils used in HPL oils. Normally ASTM D341 works very well for a monograde oil without a VII. However, for some PAO base oils, especially mPAO base stocks HPL uses, it's not clear how well ASTM D341 works.