Hello Gokhan, I can answer some of these questions for you but at the same time I will leave you with another. We do not calculate anything we publish on our data sheets. We have all of the instruments in-house required for SAE J300 and publish what we measure. We absolutely use the same batch of oil for all of the testing. It would be bad lab discipline to do otherwise. You are correct that both our SAE 20 as well as our 10W20 are monogrades with no VI Improver. What we are experiencing is a real but not yet explained synergy in our formulation. We have repeated the tests (again with the same batch) ant the results repeat. We have run the standards through our instruments to verify the calibration another are right on the money. There definitely is a discrepancy from D-341 vs what we are actually measuring. So the real question is what is the synergistic relationship that is working in our favor? I cannot yet answer that question but it does repeat in our lab. David
Originally Posted by Gokhan
Obviously for a monograde oil, A_Harman index ~ 1 and VII = (1âˆ’A_Harman index) âˆ• 2 ~ 0. HPL PCMO 20W-50 has VII ~ âˆ’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.
Originally Posted by bulwnkl
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.