Originally Posted By: OVERKILL
Originally Posted By: Joe90_guy
In theory it should all go inline with the temperature of the corresponding Cold Cranking Simulator (CCS) test which defines the minimum temperature for turning the engine crackshaft over. This reads as.
for 10WXX, -25C
for 5WXX, -30C
for 0WXX, -35C
There's another test called the Mini-Rotary Viscometer (MRV) test that also gets run on oils. This always gets run at 10C below the corresponding CCS temperature, the idea being that the oil will NOT be gellified into a waxy solid at or above this temperature.
It's 5C below the CCS temp; CCS @ -35C, MRV @ -40C
And yes, the MRV test is designed to replicate the ability for the oil to pump and it has a much higher limit on viscosity than CCS.
Thanks OVERKILL, you planted something the other day that has finally sprouted...not a eureka moment by any stretch.
You'll probably recall that I've been chasing a "high shear" Viscosity index, about since that Supertech oil product data sheet lobbed complete with an "High shear" 100 viscosity.
Also, I've questioned why for a given HTHS, the uber high VIs of the Japanese OEMs seem counterproductive in that they have a high KV value for a given "level of protection" (HTHS), and seem therefore wasteful of energy when it comes to simple pumping.
CCS is a cranking simulator, and has a "high shear" rate, 10^4 or thereabouts.
MRV is supposed to be how the engine oil makes it to the pickup, and through the pickup tube. It's shear stress is 500-1000 times lower than CCS, so shear rates are similarly lower.
And as you point out, the MRV is much larger than the CCS, about 10 times, for a 5 degree change.
Got me thinking about temporary shear at high shear rates (HTHS versus KV - Harmann Index if you will), and the next obvious conclusion.
The CCS and MRV give an indication of the action of polymeric VIIs at the extreme cold end of the equation.
Check out these Mobil oils
https://mobiloil.com/en/motor-oils/mobil-super/mobil-super-synthetic
See the CCS/MRV change with VII treat rate...Big difference between the 0W20 and 5W20, and the 5W30 and 10W30.
Look up some 20W20 dino sheets, and the non VIIed oils are much much closer in MRV/CCS than the polymer boosted oils...obviously a 20W20 isn't the oil for a -35C morning, but the polymers that give the 0W20 it's VI aren't helping the oil get through the pickup tube.