Originally Posted by Garak
Oh yes, I understand what you mean, but my issue isn't so much there. There can be problems with interpolations, but at least we do have a lot of KV40 and KV100 values in reality from data sheets and VOAs. When it comes to the KV150 business, that's where I really wonder. Out of interest's sake, I might play with some of those numbers you suggested if I can get a few free minutes.
ASTM D341 certainly claims validity for 150 C. Here is the official range claimed:
3 | Technical Hazard
3.1 Warning—The charts should be used only in that range in which the hydrocarbon or petroleum fluids are homogeneous liquids. The suggested range is thus between the cloud point at low temperatures and the initial boiling point at higher temperatures. The charts provide improved linearity in both low kinematic viscosity and at temperatures up to 340â€Â°C (approximately 650â€Â°F) or higher. Some high-boiling point materials can show a small deviation from a straight line as low as 280â€Â°C (approximately 550â€Â°F), depending on the individual sample or accuracy of the data. Reliable data can be usefully plotted in the high temperature region even if it does exhibit some curvature. Extrapolations into such regions from lower temperatures will lack accuracy, however. Experimental data taken below the cloud point or temperature of crystal growth will generally not be of reliable repeatability for interpolation or extrapolation on the charts. It should also be emphasized that fluids other than hydrocarbons will usually not plot as a straight line on these charts.
Regarding the effect of the VII, emod's Lubrizol article says that for the OCP (olefin copolymer) VII, which is by far the most common VII because of its resistance to form turbocharger deposits, the KV is multiplied by the same proportion independent of the temperature. Therefore, if ASTM D341 already works for a given base oil, it should work well when an OCP VII is added.
That leaves only the detergent inhibitor (DI) package to worry about but the effect of that on the viscosity should be relatively minor and the temperature variation of the effect of the DI should be accounted by the calculation to a fair degree.
An interesting note is that since the OCP VII effectively multiplies both the KV40 and KV100 by the same number, this increases the resultant VI. For a given starting VI, the effect of a given OCP VII content on the VI is greater for smaller KV100 values (thinner base oils).
Oh yes, I understand what you mean, but my issue isn't so much there. There can be problems with interpolations, but at least we do have a lot of KV40 and KV100 values in reality from data sheets and VOAs. When it comes to the KV150 business, that's where I really wonder. Out of interest's sake, I might play with some of those numbers you suggested if I can get a few free minutes.
ASTM D341 certainly claims validity for 150 C. Here is the official range claimed:
3 | Technical Hazard
3.1 Warning—The charts should be used only in that range in which the hydrocarbon or petroleum fluids are homogeneous liquids. The suggested range is thus between the cloud point at low temperatures and the initial boiling point at higher temperatures. The charts provide improved linearity in both low kinematic viscosity and at temperatures up to 340â€Â°C (approximately 650â€Â°F) or higher. Some high-boiling point materials can show a small deviation from a straight line as low as 280â€Â°C (approximately 550â€Â°F), depending on the individual sample or accuracy of the data. Reliable data can be usefully plotted in the high temperature region even if it does exhibit some curvature. Extrapolations into such regions from lower temperatures will lack accuracy, however. Experimental data taken below the cloud point or temperature of crystal growth will generally not be of reliable repeatability for interpolation or extrapolation on the charts. It should also be emphasized that fluids other than hydrocarbons will usually not plot as a straight line on these charts.
Regarding the effect of the VII, emod's Lubrizol article says that for the OCP (olefin copolymer) VII, which is by far the most common VII because of its resistance to form turbocharger deposits, the KV is multiplied by the same proportion independent of the temperature. Therefore, if ASTM D341 already works for a given base oil, it should work well when an OCP VII is added.
That leaves only the detergent inhibitor (DI) package to worry about but the effect of that on the viscosity should be relatively minor and the temperature variation of the effect of the DI should be accounted by the calculation to a fair degree.
An interesting note is that since the OCP VII effectively multiplies both the KV40 and KV100 by the same number, this increases the resultant VI. For a given starting VI, the effect of a given OCP VII content on the VI is greater for smaller KV100 values (thinner base oils).
