I have now fully automated my A_Harman index, effective VII content, and base-oil viscosity calculator by building in the ASTM D341 viscosity - temperature relation (Walther formula) into the spreadsheet.
If you want to calculate these values for an oil, you can either (a) make a copy of the Google sheet or (b) download it as an Excel file from the File menu so that you can edit and work on it:
>> Estimated base-oil viscosity @ 150 °C (BO DV150) and VII content of selected oils a>
Input values needed (gold columns):
Output calculated (green columns):
The most remarkable output of the calculator is the base-oil viscosity (full-shear viscosity) at 150 °C (BO DV150 = HTFS), which applies to the valvetrain, timing-chain, piston-ring, and cylinder-liner wear since the oil goes through full shear in these engine components, whereas the HTHS (high-shear viscosity) applies to the bearing wear since the oil goes through high shear but not full shear in the bearings.
Important notes: The base-oil viscosity includes both the base oil and detergent - dispersant - inhibitor (DDI) package. Some base oils, such as POE base stocks and high-viscosity PAO base stocks, temporarily shear like a VII and may appear as an effective VII content in the calculation.
Note that I have also improved the accuracy of the calculator by accounting for the ASTM D341 underestimation of KV150 using a slightly higher density correction factor (0.917) when calculating DV150.
You can read the theory and discussion in the thread below. I have recently verified the accuracy of the base-oil-viscosity calculator against the test oils in the Hugh Spikes paper, which can be found at the end of this theory thread:
[URL='https://www.bobistheoilguy.com/forums/ubbthreads.php/topics/5133403/re-htfsv-high-temperature-full-shear-viscosity#Post5133403']HTFS: high-temperature, full-shear viscosity
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If you want to calculate these values for an oil, you can either (a) make a copy of the Google sheet or (b) download it as an Excel file from the File menu so that you can edit and work on it:
>> Estimated base-oil viscosity @ 150 °C (BO DV150) and VII content of selected oils a>
Input values needed (gold columns):
- oil name (info only)
- density at 60 °F (15.6 °C) (g/cm³)
- KV40 (cSt)
- KV100 (cSt)
- VI (info only)
- HTHS (cP) (high-temperature, high-shear viscosity)
Output calculated (green columns):
- A_Harman index: a measure of the effective viscosity-index improver (VII) content through the temporary shear of the oil
- VII content: effective VII content (measured by the temporary shear, not the actual solid or oil-solvent-dissolved VII content) directly given by the A_Harman index
- BO DV150 (HTFS) (cP): base-oil (plus the additive package) viscosity at 150 °C excluding the VII -- high-temperature, full-shear viscosity -- directly given by the A_Harman index and HTHS
The most remarkable output of the calculator is the base-oil viscosity (full-shear viscosity) at 150 °C (BO DV150 = HTFS), which applies to the valvetrain, timing-chain, piston-ring, and cylinder-liner wear since the oil goes through full shear in these engine components, whereas the HTHS (high-shear viscosity) applies to the bearing wear since the oil goes through high shear but not full shear in the bearings.
Important notes: The base-oil viscosity includes both the base oil and detergent - dispersant - inhibitor (DDI) package. Some base oils, such as POE base stocks and high-viscosity PAO base stocks, temporarily shear like a VII and may appear as an effective VII content in the calculation.
Note that I have also improved the accuracy of the calculator by accounting for the ASTM D341 underestimation of KV150 using a slightly higher density correction factor (0.917) when calculating DV150.
You can read the theory and discussion in the thread below. I have recently verified the accuracy of the base-oil-viscosity calculator against the test oils in the Hugh Spikes paper, which can be found at the end of this theory thread:
[URL='https://www.bobistheoilguy.com/forums/ubbthreads.php/topics/5133403/re-htfsv-high-temperature-full-shear-viscosity#Post5133403']HTFS: high-temperature, full-shear viscosity