Paper the Expansding Dimensions of High Shear Viscometry.
http://www.savantlab.com/images/TBS_Paper_-_SAE_2008-01-1621_The_Expanding_Dimensions....pdf
As some of you know, I've been trying to get a handle on what the viscosity index in the high shear regime is for just about ever, not to a great deal of success.
This is another Selby paper, which is a typical go to for good guts work.
Explains the role of VIIs, and how they work, and has this chart...
It's a range of multigrade engine oils from the US, on the LHS axis is the temporary viscosity loss at 150C high shear conditions, and on the bottom axis is the same shear rate at 100C. Temporary viscosity loss is the delta in viscosity with high shear rate, as the polymeric VIIs get stretched with increasing shear rate.
For those following along it's precisely (1- the Harman Index)
It appears looking at the chart that the loss of viscosity due to high shear at 100C is about 1-1/2 times the loss at 150C (Paper says 30% more, but chart looks steeper).
There's an explaination for that. Remember that multigrades are typically a lighter base-stock, with VII added. There are two phenomenon at play here.
1) the temperature is lower, so the VII aren't as fluffy, and therefore have less impact in increasing the viscosity.
2) the oil is thicker, drags the polymers more, and they flatten out earlier.
So the high shear at lower temperatures is even closer to the base oil viscosity than at 150C.
Yonks ago, someone posted a supertech 5W30 data sheet, which had the rare gem of HTHS 100C
https://bobistheoilguy.com/forums/ubbthreads.php/topics/3307068/Walmart_SuperTech_Synthetic_sp
So messing with it, and this chart, I calculated a few things (black is source data, pink is calculated). I've included the calculators that I always use to calculate density and viscosity on it.
So the high shear 100C viscosity is about 60% more at 100C than at 150C...about consistent with the chart.
What does this mean ?
That the High Shear Viscosity Index, as it relies on both the base oil (Newtonian VI), and the changing nature of VIIs with both temperature and shear rate...is actually higher than the kinematic viscosity index...
http://www.savantlab.com/images/TBS_Paper_-_SAE_2008-01-1621_The_Expanding_Dimensions....pdf
As some of you know, I've been trying to get a handle on what the viscosity index in the high shear regime is for just about ever, not to a great deal of success.
This is another Selby paper, which is a typical go to for good guts work.
Explains the role of VIIs, and how they work, and has this chart...
It's a range of multigrade engine oils from the US, on the LHS axis is the temporary viscosity loss at 150C high shear conditions, and on the bottom axis is the same shear rate at 100C. Temporary viscosity loss is the delta in viscosity with high shear rate, as the polymeric VIIs get stretched with increasing shear rate.
For those following along it's precisely (1- the Harman Index)
It appears looking at the chart that the loss of viscosity due to high shear at 100C is about 1-1/2 times the loss at 150C (Paper says 30% more, but chart looks steeper).
There's an explaination for that. Remember that multigrades are typically a lighter base-stock, with VII added. There are two phenomenon at play here.
1) the temperature is lower, so the VII aren't as fluffy, and therefore have less impact in increasing the viscosity.
2) the oil is thicker, drags the polymers more, and they flatten out earlier.
So the high shear at lower temperatures is even closer to the base oil viscosity than at 150C.
Yonks ago, someone posted a supertech 5W30 data sheet, which had the rare gem of HTHS 100C
https://bobistheoilguy.com/forums/ubbthreads.php/topics/3307068/Walmart_SuperTech_Synthetic_sp
So messing with it, and this chart, I calculated a few things (black is source data, pink is calculated). I've included the calculators that I always use to calculate density and viscosity on it.
So the high shear 100C viscosity is about 60% more at 100C than at 150C...about consistent with the chart.
What does this mean ?
That the High Shear Viscosity Index, as it relies on both the base oil (Newtonian VI), and the changing nature of VIIs with both temperature and shear rate...is actually higher than the kinematic viscosity index...