Qualities of mixed viscosity oils ?

[CITYSLICKER]

Another thread made me start thinking ( usually not a good thing )

Supposing A very thick oil ( 250w? ) and a very thin oil ( 5W? ) were blended to a
vis. approximating that of 40W oil .

How would the qualities of this blend differ from that of a similar viscosity blend made from
oils much closer to each other in vis. ?

This doesn't actually pertain to any specific application , just a question to
further my understanding.

I would assume the end results would be pretty different due to the longer chains
inherited from the thicker base oil ?

 

[Pablo]

Really depends on how the 250W was made....if you leave VII's out of it, it's not so complex.

 

[bruce381]

depends thats called a "dumbell blend"
in your example compared to a striaght oil of the 40w the blend would have

higher film strength from the heavy oil
higher volitlity from the light oil
higher pour point form the heavier oil

something like that
bruce

 

[Tempest]

Would the lighter fractions tend to impart more solubility?

 

[Gary Allan]

Quote:
thats called a "dumbell blend"


Yes. Flexblend®

Great for owners of oil consuming engines in 4 season climates. Just add up or down as the climate allows ...targeting optimum, best case, consumption. A micromanaged solution for those who are looking for problems.

 

[CITYSLICKER]

Pourpoint .

Thats where I was headed in the wrong direction .

I failed to make the distinction between pourpoint and viscosity .

I guess theres no free lunch .

Just for giggles , can anybody explain the vis. vs. pourpoint thing ?

 

[CITYSLICKER]

Better yet ,
If anyone can explain the relationship between viscosity , pour point , and breakaway torque ( without making my head explode ) I would appreciate it .

 

[bruce381]

""Would the lighter fractions tend to impart more solubility?""

yes

 

[bruce381]

Originally Posted By: CITYSLICKER
Better yet ,
If anyone can explain the relationship between viscosity , pour point , and breakaway torque ( without making my head explode ) I would appreciate it .


Normally for a given base oil the higher the vis the higher the density and HIGHER the pour point.

Diferent base oils have diferent pour points depending what they are a PAO has NO wax so PP is very low a parrafinic oil may have wax and has a higher PP.

"breakaway" torque is usally for a grease and is mesured in a tapered bearing like a wheel bearing at varying COLD temps forgot what tho anyway a whatever cold temp the TORQUE that it takes to GET THE bearing moving is "breakaway".

get some cheap roller bearings and pack with whatever grease you want put in a plactic bag put in freezer take out over night and turn bearing you will understand breakaway torque real quick.

Normally high vis oils and/or oils with BAD PP will when used in grease will affect torque so will soap thickener type.

As I remember best thickener is silica and/or bentone clay or poly urea, best oil is low vis PAO some esters or Napthenic oils which all have LOW PP. Soap thickeners like AL or LI tend to get harder when cold and as such will have high torque values.

bruce

 

[CITYSLICKER]

It's starting to make more sense .
I think ...

All other things being equal between two blends :

the blend with the higher viscosity oil would have a higher percentage of vis. increase when cold ?

 

[bruce381]

yes

 

[CITYSLICKER]

I actually did some hands on research .

Absolutely no need for sophisticated test equipment to feel the difference .

Thanks for steering me in the right direction !

This probably falls under the heading of " DUH ! " to some , but it's new to me .