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. Important notes: The base-oil viscosity includes both the base oil and detergent - dispersant - inhibitor (DDI) package. The most remarkable output of the calculator is the base-oil viscosity (full-shear viscosity) at 150 Â☌ (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. BO DV150 (HTFS) (cP): base-oil (plus the additive package) viscosity at 150 Â☌ excluding the VII - high-temperature, full-shear viscosity - directly given by the A_Harman index and HTHS.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.A_Harman index: a measure of the effective viscosity-index improver (VII) content through the temporary shear of the oil.HTHS (cP) (high-temperature, high-shear viscosity).
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 Â☌ (BO DV150) and VII content of selected oils << 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.
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