If you really want to know about the theoretical background, read the threads on the subject and try to understand them instead of bickering about the validity of the deep technical aspects that are obscure to you.
The base-oil viscosity (high-temperature, full-shear (HTFS) viscosity) calculations were fully tested and verified against the test oils in the Hugh Spikes paper, and recently "another member" Boxnuts with a strong technical background helped me go over them and question certain things, which has improved the calculation:
I have showed the other tool -- the base-oil quality index (BOQI) -- to indeed predict the base-oil type of most known oils with Group I - Group IV base oils. The notion of a CCS - Noack space is well-established "in the industry," and it is frequently used. I only turned the existing notion into a simple quantitative tool. For example Group IIIa, IIIb, IIIc, and IIId oils ascending in the base-oil quality are clearly distinguished in the CCS - Noack space. You can see where in the industry it is coming from:
Even more interestingly Shannow had criticized that the lower-viscosity PAO base stocks tend to have a higher BOQI than the higher-viscosity PAO base stocks, but there was recently a very nice article about synthetic base stocks in the Lubes'n'Greases magazine, and it showed that the oxidation time, which is the primary measure of the base-oil quality, is indeed inversely proportional to CCS Ã— Noack. The old and new PAO base stocks have almost the same Noack, but the new PAO base stock has a much lower CCS, which results in a higher BOQI ~ 1 / (CCS Ã— Noack) and a proportionally higher oxidation time -- quantitatively verified by ExxonMobil: