I think some of the clues that Shannow is looking for may be found in
the Lubrizol site.
They mention a spike in demand for shear stable friction modifiers for
HDMOs and other applications.
Additive packages that alter the viscosity behavior of a lubricant
may slip through cracks in the mono-grade rule of no VIIs.
It may be a possibility that the rules only applied to a type of VII,
and not all the VIIs that have been invented since the rule was written.
For the purpose of this discussion, lets assume that any additive that changes the
viscosity behavior of a fluid is a VII.
Would it be possible to render down hours of reading to a few items that all agree on?
Duron-E in gas engine?
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shear stable has two facets...temporary shear, which is the non newtonian bit when thy thin at high shear rates, to an apparent new viscosity, but recover when the shear rate goes back down...the reason for HTHS being introduced into J300.
The second is permanent shear, which is the VII molecules being torn up, reducing both the KV AND the HTHS, permanently...that's the "shear stability" that is typically referred to in the search for better VIIs.
OK, to avoid my apparent confusion, I'll defer to SAE J300
http://paservice.it/wp-content/uploads/2013/06/J300_201304.pdf
they are saying that to carry the straight weight label, they must be newtonian, e.g. the viscosity at 150C is the same when running by gravity through a drop tube as it is in a rotary viscometer at 10^6 shear rate.
PAO increases the VI of an oil , but does not display the behaviours of those chemicals that are expressly employed to provide VII...they display characteristics in mixing (and they are blended in the single digit fractions like tenths, quarter and halves), not added in small percentages to affect great changes (like doubling the KV100 with a couple of percent), which is the role of VII polymers.
Originally Posted By: used_0il
For the purpose of this discussion, lets assume that any additive that changes the viscosity behavior of a fluid is a VII.
Quote:
Many commercial engine oils contain polymeric additives for a variety of purposes, one of the most important of which is viscosity modification. Specifically, the use of such additives in creating multigrade oils is commonplace. However, oils containing a significant polymeric additive concentration, whether for viscosity modification or another lubricant function, are generally characterized by having a non-Newtonian, “shear thinning” viscosity (i.e., a viscosity which decreases with increasing shear rate).
Quote:
Most oils will meet the viscosity requirements of at least one of the W grades. Nevertheless, consistent with historic practice, any Newtonian oil may be labeled as a single-grade oil (either with or without a W). Oils which are formulated with polymeric viscosity index improvers for the purpose of making them multiviscosity-grade products are non-Newtonian and must be labeled with the appropriate multiviscosity grade (both W and high-temperature grade).
Don't confuse me with facts.
I just read recently on here, somewhere, that the viscosity of air increases
with temperature rise.
The Bullet and the Windmill
Farmer Brown noticed that his windmill turned faster on hot days than on cold days.
Because the day was hot, he went hunting instead of working on the farm.
The plains animals took shelter from the wind and heat in the valleys, so that
is where farmer Brown went hunting.
Farmer Brown noticed that on these hot days, his bullets traveled faster and further.
Farmer Brown came to the conclusion that on hot days the viscosity of the air is
higher, but the shear rate is lower.
As silly as it may sound, that is everything you said.
I'll try your way another way.
The viscosity of a fluid increases with higher temperatures.
The shear rate is reduced with higher temperatures.
We measure shear (Cst) and assume that we are measuring viscosity.
The viscosity and shear are actually going in opposite directions with temperature change.
Shear wins, viscosity loses.
Viscosity decreases as temperature increases.
When the last trace of shear is lost in the medium we are discussing,
fluidity is lost and what once a liquid, is now a gas.
If Newtonian laws all require a time reference, then his laws cannot apply
to a liquid at rest.
Pulling a sled through a liquid at rest then inventing new rules to prove
a point is not science, its convenience.
The rate which a fluid at temperature flows under it's own gravity is one thing.
A fluid that is pumped, by positive displacement or any other means including the
bearing on a rotating shaft-
Acts and behaves like a solid.
Viscosity, whatever it is, counts for nothing.
So far the oil has left the pump, and since it is not compressible
acted like a solid.
Pressure is a reaction or the resistance, a dead horse at this point.
The engine is like a leaky garden hose.
Once the oil has gotten to where it is needed, it turns back into a liquid from a solid
and leaked at a controlled rate.
As the lubricant heats up, the leakage increases requiring a greater supply.
Up to this point, the only role increased fluidity has affected is increased leakage.
Nothing has changed on the supply side, because so far the pump has kept up with demand.
From the supply side, pressure and fluidity is still a non-issue.
If we spend another week discussing hydrodynamic, supply, demand and lubrication,
and ignore the other three, ( elasto-hydrodynamic, boundary and mixed) then we are
wasting our and other peoples' time.
Originally Posted By: used_0il
When the last trace of shear is lost in the medium we are discussing,
fluidity is lost and what once a liquid, is now a gas.
If Newtonian laws all require a time reference, then his laws cannot apply
to a liquid at rest.
Originally Posted By: used_0il
The rate which a fluid at temperature flows under it's own gravity is one thing.
A fluid that is pumped, by positive displacement or any other means including the bearing on a rotating shaft-
Acts and behaves like a solid.
Viscosity, whatever it is, counts for nothing.
The definition of work requires a time element too.
The wear test ultimately would be the only variable that really mattered, everything
else, moot points.
Connecting the dots from what we have and how we got there is the process.
So far we have supplied a solid column of oil to the galleries in
engine.
Among other things, your automotive engine is a stove and a wash machine.
To keep the stove at a constant temperature and from overheating, oil is used
as a liquid coolant.
To keep the stove clean, the same oil is used.
The oil flow through the hydrodynamic (plain) bearings cools and lubricates them.
Increased fluidity from the oil temperature rising, the use of a lighter grade
of oil or both, increases leakage from the hydro dynamically lubricated bearings.
AS long as the oil supply is sufficient, the pressure that it is delivered is immaterial.
(So yes, to the first question.)
Next on the list is boundary lubrication.
Our hot lubricant is now more fluid than when cold, cleaning and cooling the engine.
The plain bearings are doing just fine.
The leakage is high from those bearings and the oil is thrown, dripped and sprayed to
other parts of the engine.
Removing heat, cleaning and lubricating all the parts that need cooling, cleaning
and lubricating, better than when the oil was cold and bearing leakage was less.
Because during boundary lubrication there is not a film of oil separating engine
parts, anti wear additives have to make up the difference.
Now the engine oil has taken a role of a coolant, cleaner and an additive delivery
system.
This is where a lighter more fluid lubricant does a better job, by providing
better engine lubrication through higher volume than a thicker oil or the
same oil when cold.
Run an engine using an electric motor, and see how "stove" like it is...and how you cannot discount work in the process.
Oil will increase in temperature all on it's lonesome (with applied work) even without fuel and fire...the temperature in the bearings increases over supply temperature by some 10s of C purely due to the work applied to it by the turning shaft...can't discount it...that's why thin oils save fuel, you do less work against them.
Your flow/wear theory is wrong...actually, that's not all that's wrong. You can look at texbooks that explain things rather than making up random esoteric nonsense.
And where's your evidence that in things like sequence IV, the ultimate test of mixed lubrication, that the thin oils are doing a "better job" ?
I didn't come to praise Caesar, (viscosity) but to bury him.
I'm trying to avoid writing a book report on a 384 page 1994
thesis on fluid dynamics.
The above questions presented and avoided with help from Shakespeare
is my way of buying time while I try and think of a story that is brief.
As I see it, there is no one size fits all approach to optimum engine oil
viscosity application.
An air cooled aircraft engine that has .007" piston clearance or the rear
cylinder of a Harley Davidson motorcycle engine, have different oil viscosity
requirements than that of a 2015 Honda Accord.
I know what non-Newtonian shear is, but I refuse to discuss the topic in the automotive
section, because it is pointless for one.
The best answer so far that I have read is that the solution is; to each his own,
or solutions unique to every vehicle owner.
The best advice on a similar topic I ever received was- Do your own research and
go with it.
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You are going to have to translate those last few posts.
Translation;
These are my opinions and nothing more.
Shannow has scored a couple of victories in the above thread that he has been
discussing for a while now.
Can you spot them?
I'll post a story that has nothing to do with anything, go for a two hour
walk and think about an answer to the challenges I created for myself.
I believe that Shannow for some time has tried to discredit the use of
"operational viscosity" and using a pressure gauge as evidence as to what is
going on inside an engine.
Convincing one person after all this time is the victory.
That gets me past the "hydro-dynamically" lubricated bearings
on our pump to sump journey.
Next is the loss of viscosity while the lubricant is in the clearance
between the bearing and journal.
Two ways which the oil gathers heat while in its tour of duty;
1. The oil picks up heat from the bearing and journal.
2. The oil warms itself through the internal friction of the lubricant.
Because of the VII action of a multi-grade engine oil, the viscosity loss
while in service will be less than a mono-grade engine oil.
Next on the pump to sump journey is boundary lubrication and its cousins.
This is why I dropped the hint a few posts ago, about a spike in demand
for shear stable friction modifiers, and throw in anti wear additives now
please.
Those additives come into play when hydro-dynamic lubrication is not present
to physically separate moving parts.
There is a graph that shows friction with and without those additives.
With additives wins.
With the continuing progress to lower viscosity engine oils to improve
fleet fuel economy targets, development of better additive packages
is necessary.
This is where I believe the "volume over viscosity" theory I threw up
there merits some consideration.
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Posted this some little while ago regarding friction in boundary.
http://www.bobistheoilguy.com/forums/ubbthreads.php/topics/3390995/Why_designers_allow_mixed_lubr
I feel for the first time progress on the topic of viscosity.
GM's lengthy discussion on the "new" 5.3L V8 stated, that to reduce parasitic
power loss, the oil pressure was reduced during certain conditions and
increased when the demand of engine oil increased.
This would suggest that there is a relationship between oil pressure and supply.
However, if I buy into your program; that using oil pressure as "evidence" that certain
conditions exist is wrong, then clarification of the two needs to be addressed.
I'm starting to believe after reading through the many threads on the viscosity
topic, that everyone is correct and nobody knows what the other member is talking about.
For some strange reason, everyone has it straight in their own heads, yet opinions
vastly differ.
If I explain why I'm thinking a certain way and how I arrived at a conclusion,
the competitiveness diminishes and I usually get the answer I'm looking for.
Sometimes we can trip over what we are looking for with "out of the box" thinking.
Solutions come when we finally accept that everything we've
done up until now is wrong, and there is a better way of doing everything.
My out of the box stories may appear "comic", I had a laugh writing them,
but the seriousness was masked.
OK...
do I beleive that CATERHAM's experiments on oil pressure/HTHS (operation viscosity) are a valid correlation ? Resoundingly YES.
do I believe that using the manufacturer's recommended maintenance oil pressure to choose a viscosity is valid (i.e. a predictor of hydrodynamic lubrication) ? NO (particularly when it's outside of OEM recommendations)
as an engineer, would I design industrial machines for full hydrodynamic lubrication ? resoundingly yes, as they are expected to be there for many hundreds of thousands of hours (and are designed also with pre-lubes, kidney loop filtration, and pre-heating (which generally has them using monogrades...the oil that I've bought more of than any other has a KV100 of 5.3, not even a 16 grade)).
as an engineer, with a car that that only needs lasting some small tens of thousands of hours, and will be thrown out typically before the engine is done, would I design boundary/mixed to minimise viscous drag during that life ? Yes.
Does High VI help in lubricant selection in all the above ? Yes, of course, it's more nearly optimum everywhere...where it doesn't make sense is if you need an HTHS of 2.6, making an oil of KV100 mid 8s, and having it lose nearly 10% of it's HTHS early in the OCI...have seen ISO32 hydraulic oils become 24, and ISO 1000 become 450 cst too often to think that chasing VI for VI sake is a worthy endeavour.
To Garak, from the flat earth society;
(Saskatchewan)
You are stopped at a red light.
You know that time has not stopped because you can see cars moving in the other direction.
I can't measure what you are doing or capable of, from the action of others.
Farmer Brown's marriage has lasted because he can fake deafness.
There are no clocks in the Brown residence, he does not own a watch.
On the days farmer Brown goes hunting, he is always late for supper.
This is because when farmer Brown is having fun, time flies.
On those same days Ms Brown is at home alone doing chores around the house and farm.
As a result the day drags on, and she has supper ready early.
When farmer Brown returns from the hunt (late and deaf), he is excited to
tell his wife of his experience.
It takes farmer Brown 30 minutes, (by Ms Brown's calculation) for farmer Brown to tell
his story.
Farmer Brown's detailed recollection of a difficult shot that took five seconds
from start to finish took ten minutes to tell.
Time slowed and almost stopped for farmer Brown at the most exciting part of his day.
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