Originally Posted By: used_0il
I'm finding a non-linear relationship between engine oils that have identical KV100 numbers, but different HTHS.
The viscosity index scale does not take this into account.
Missed that bit.
A Harman's shear calculator is a really handy thing to mess with.
http://www.bobistheoilguy.com/forums/ubbthreads.php/topics/3552113/Re:_Viscosity_spread_&#Post3552113
Straights (naturally) get close to 1.
CATERHAM has stated that there's a high shear rate viscosity index, that responds to VII the same as the KV does. I can't agree, as the high shear "second Newtonian" period under high shear rates is when the polymers line up to vastly reduced effect (KV versus HTHS).
Haven't been presented with, nor found any proof, nor opposition papers, so am keeping an open mind.
However, I HAVE used the Walmart Supertech PDS, which has a High shear rate 100C...
here KV100 is 11.2, HTHS 100 7.26, HTHS 150 3.17
With Widman's operational viscosity calculator, using the HTHS 100 and 150 viscosities to "calculate" an HTHS 40 of 45.11 (KV40 64.33).
Gives a "High Shear" Viscosity Index of 123 (versus the Kinematic 165 of the finished oil) which while being an estimation off a calculation would support my belief that the VII doesn't modify the high shear Viscosity Index...123 is pretty darned close to what the "synthetic" basestocks would bring to the table in the first place.
Your "high shear" viscosity index in your blend could be comparable to TGMO...maybe.