variations in reported pour points of a motor oil

[SonofJoe]

Originally Posted By: Shannow
Great question...

now I know I'm staying up late after we go out for mother's day dinner.

(CCS SHOULD drop if the VIIs shear, and we do know that adding fuel to the sump aids starting in aircraft)


I've not done the experiment but I'd guess that CCS would not drop with VII shearing. KV100, KV40 and possibly even KV10 would definitely drop but generally when you go down to CCS temperatures, the VII molecules are so scrunched up, they're not really acting as VI improvers any more.

 

[Shannow]

I'm quietly confident that the VIIs still play a part down there...

I'll wheel out the old Mobil blend guide for discussion.

Using the rule of thumb that at the bottom end of the temperature scale viscosity doubles every 5 degrees drop, and that fortunately down there, they are Cp, not Cst, AND that CCS is a "high shear rate" tests while MRV is relatively quiescent.

In a Newtonian fluid the shear rate shouldn't therefore change the ratio away from MRV is double the CCS (yes rule of thumb, not exact).

Looking that the above, the lubes with around 2.5 to 3% VM treat are at 2 (and a bit). The 7 to 9 are a bit under 3, and the 11ses over 3.

So it appears that the VII molecules are still doing some stuff down at the extreme end.

Also, given that their effectiveness is lower in thicker oil, the second newtonian for those oils is a couple of orders of magnitude lower than the 10^6s^-1 of the HTHS.

 

[merconvvv]

Those are some good blends. Too bad they dont make them.
Did they ever sell anything close to that over the years?
At the consumer end there is a lot of info missing for products on the shelf.

I was so frustrated few months back i even looked up prices for one drum of spectrasyn 8 and 10 to see if i can blend my own. lol

 

[Shannow]

Maybe Joe can hook you up with an additive package when you get your drum of spectrasyn.