CCV and MRV significance

[KrisZ]

Straight from the ASTM website:
Quote:
CCS apparent viscosity is not suitable for predicting low temperature flow to the engine oil pump and oil distribution system.

Quote:
A correlation was established in a low temperature engine performance study between light duty engine startability and CCS measured apparent viscosity. This study used ten 1990s engines at temperatures ranging from –5 °C down to –40 °C with six commercial engine oils (SAE 0W, 5W, 10W, 15W, 20W, and 25W).8


It is a rough estimation for the cold engine startability. CCV should by no means be used as the basis for cold oil performance, it is written right in the spec. Why? Only the apparatus is cooled down to the reference temperature. Then the oil is poured in and the test begins after 90 seconds.

Now lets see what the MRV test has to offer:
Quote:
When an engine oil is cooled, the rate and duration of cooling can affect its yield stress and viscosity. In this laboratory test, a fresh engine oil is slowly cooled through a temperature range where wax crystallization is known to occur, followed by relatively rapid cooling to the final test temperature.

Quote:
These laboratory test results have predicted as failures the known engine oils that have failed in the field because of lack of oil pumpability


Now, this is a much better test to represent true cold starting conditions. The oil is actually cooled down for over 45 hours to ensure the oil properly reacts to the low temperature. Not only that, the test was clearly developed to deal with engine failures due to the inability of the oil to be pumped.

 

[Shannow]

Originally Posted By: KrisZ
Now lets see what the MRV test has to offer:
Quote:
When an engine oil is cooled, the rate and duration of cooling can affect its yield stress and viscosity. In this laboratory test, a fresh engine oil is slowly cooled through a temperature range where wax crystallization is known to occur, followed by relatively rapid cooling to the final test temperature.

Quote:
These laboratory test results have predicted as failures the known engine oils that have failed in the field because of lack of oil pumpability



Now, this is a much better test to represent true cold starting conditions. The oil is actually cooled down for over 45 hours to ensure the oil properly reacts to the low temperature. Not only that, the test was clearly developed to deal with engine failures due to the inability of the oil to be pumped.



WE had some (brief discussion about the origins here

 

[xtell]

For a novice on oil formulations, would MRV specifications, when looking for a good flowing cold temperature oil, be the main specification that one should focus on versus CCV and low temp pour point? Also, I know that HT/HS is a specification for hot oil, but how much of a factor would the shear rate of oil have when considering low temperature oil performance?

xtell

 

[Tom NJ]

CCS and MRV measure different oil properties. The CCS test measures the ability of the oil to be picked up and pumped by the oil pump under shear stress. MRV measures the ability of the oil to flow under its own weight back into the hole sucked out by the oil pump.

Think of Jell-O. Jell-O can be easily sucked up and pumped by a mechanical pump, in fact you can suck it up through a straw. But once pumped the remaining Jell-O will not flow back to fill the hole, and the pump (or straw) will now suck air. Jell-O, like many oils, has a weak crystalline structure that can be easily overcome by applying shear, but without such external mechanical force it cannot flow.

Both tests are influenced by viscosity and wax crystal growth/pattern, but they differ in shear rate, i.e. higher shear pumping versus lower shear flowing. The actual conditions under which the tests are run were developed to correlate with known oil performance observed in the field and has proved very useful over the years.

I would consider CCS to be less critical than MRV since modern oil pumps are quite capable and efficient. The factors that influence MRV are more elusive and sometimes unexpected issues arise during formulation.

Tom NJ

 

[OVERKILL]

Originally Posted By: Tom NJ
CCS and MRV measure different oil properties. The CCS test measures the ability of the oil to be picked up and pumped by the oil pump under shear stress. MRV measures the ability of the oil to flow under its own weight back into the hole sucked out by the oil pump.

Think of Jell-O. Jell-O can be easily sucked up and pumped by a mechanical pump, in fact you can suck it up through a straw. But once pumped the remaining Jell-O will not flow back to fill the hole, and the pump (or straw) will now suck air. Jell-O, like many oils, has a weak crystalline structure that can be easily overcome by applying shear, but without such external mechanical force it cannot flow.

Both tests are influenced by viscosity and wax crystal growth/pattern, but they differ in shear rate, i.e. higher shear pumping versus lower shear flowing. The actual conditions under which the tests are run were developed to correlate with known oil performance observed in the field and has proved very useful over the years.

I would consider CCS to be less critical than MRV since modern oil pumps are quite capable and efficient. The factors that influence MRV are more elusive and sometimes unexpected issues arise during formulation.

Tom NJ


Thank you for the detailed explanation Tom

 

[Oil Changer]

Tom is the oil guy.

 

[147_Grain]

Originally Posted By: Oil Changer
Tom is the oil guy.

Thank-you Tom for explaining technical terms in an easy to understand way. Well said!

 

[KrisZ]

The detail that has me questioning the CCS test is why keep the apparatus at the target temp. and only allow the oil 3 minutes in there before the test begins?

 

[Tom NJ]

Originally Posted By: KrisZ
The detail that has me questioning the CCS test is why keep the apparatus at the target temp. and only allow the oil 3 minutes in there before the test begins?


The CCS is an old test, developed in 1964 - I used to run them back in the 70s. I don't know the rational behind the original development of test conditions, but I do know such tests are carefully scrutinized by the industry for correlation to known field performance before acceptance into specifications.

The test uses a small quantity of oil, and with agitation it can easily reach test temperature in three minutes.

Tom NJ

 

[KrisZ]

Thanks Tom for your input.

However I still can't wrap my head around your post that the CCS test represents the oil ability to be picked up by the pump. It's just a rotor spinning at certain RPM and the resistance is measured, or was it energy consumption? I can't remember. Yes, it applies shear stress to the oil, but the oil does not have to flow or be moved by the rotor.

It's a positive displacement pump, it will pick up rocks if they're small enough, so to me it would make sense to see if it can be rotated, that's it.

It's a great discussion BTW

 

[Jetronic]

I would like the oil to go to the oil filter and through the filter media aswell, and not out of the oil pump pressure relief valve or the oil filter bypass valve. CCS becomes a bit more important there.

 

[Shannow]

Originally Posted By: KrisZ
Thanks Tom for your input.

However I still can't wrap my head around your post that the CCS test represents the oil ability to be picked up by the pump. It's just a rotor spinning at certain RPM and the resistance is measured, or was it energy consumption? I can't remember. Yes, it applies shear stress to the oil, but the oil does not have to flow or be moved by the rotor.

It's a positive displacement pump, it will pick up rocks if they're small enough, so to me it would make sense to see if it can be rotated, that's it.

It's a great discussion BTW

KrisZ, the test is supposed to assist in demonstrating that the oil can get to the pump...I agree, and promote that provided the oil is of sufficiently low "W", the pump will shift it's said volume.

The two failure modes that exist are that the pump pumps out a hole in the nearly solid oil, and the oil can't flow in quickly enough to replace it...if you look at the J300, it mentions "with no yield stress"...it mustn't form a "cliff" to collapse, it must flow and fill up the voids.

The second failure is that it's too viscous in the pick-up tube, and the pump literally pulls more oil than the tube can supply, pulling a void (take a syringe half filled with water, and pull the plunger...you will feel resistance, then it will spring as you pull a vacuum/void in the liquid).

These are the reasons for the test, to ensure that the sump of oil can flow into the pick-up...which the pump will move in typically positive displacement manner...

The changes that were made were due to some oils responding differently to snap cooling versus long slow cooling, where the waxes interacted.

 

[Oil Changer]

This forum has lost it's spirit. We have a great question, in a relevant time of year to be asking it, we have two industry experts responding, yet it only has 600 views and might not even be on the front page of some members computers.

Concurrently, we have at the top of the page another "vs." thread with 2000 views and an OCI argument with over 1000.

I thank Tom NJ and Shannow for taking the time.

 

[KrisZ]

Originally Posted By: Oil Changer
I thank Tom NJ and Shannow for taking the time.


+1000 thanks guys for your thoughtful posts. I still have to fully read the paper Shannow linked in his first reply, I thinks it goes over the pros and cons of each testing methodology.

 

[d00df00d]

Originally Posted By: Oil Changer
This forum has lost it's spirit. We have a great question, in a relevant time of year to be asking it, we have two industry experts responding, yet it only has 600 views and might not even be on the front page of some members computers.

Concurrently, we have at the top of the page another "vs." thread with 2000 views and an OCI argument with over 1000.

I thank Tom NJ and Shannow for taking the time.

Very well said on all points.

 

[Shannow]

Member CT8 posted a link to the Esso cold temperature videos
here.

If you go to around the 8 minute mark, you can see what I'm referring to as the "pumpability"...they have a sump, and you can see oil movement (or lack of it).

 

[dustyroads]

Originally Posted By: Shannow
Member CT8 posted a link to the Esso cold temperature videos
here.

If you go to around the 8 minute mark, you can see what I'm referring to as the "pumpability"...they have a sump, and you can see oil movement (or lack of it).


I stumbled onto those videos last year and it made me cringe (to say the least). Nice thread KrisZ...I enjoy this type of thing.

 

[Lex94]

"This forum has lost it's spirit"

Someone like Shannow will post a link to a scientific study and the thread will get about 7 comments..."What oil for a 1982 Oldsmobile" thread will get 1000 comments all at the same level as "this beer taste better than that beer".

 

[virginoil]

Originally Posted By: Lex94
"This forum has lost it's spirit"

Someone like Shannow will post a link to a scientific study and the thread will get about 7 comments..."What oil for a 1982 Oldsmobile" thread will get 1000 comments all at the same level as "this beer taste better than that beer".


Agreed. I would say it loses focus from time to time.

We are fortunate some long time knowledgeable members have stuck around and and continue to contribute.

 

[virginoil]

above continued

In those days Internet was slower however response to technical threads were fast. Some debates were so heated that some members left the forum for a while to cool down (some didn't return) but the fire of passion for knowledge didn't wither.

We have so much knowledge on this board today only if there was a better search function, it could be turned into a library.

In my view the current search function "sucks" and is of poor value compared to some other forums.

A proper search function would probably get rid of the duplicated posts that are rehashed in one form or another eg 3000 mile oci or syn v mineral.

The previous threads should be easily found, navigated through, filtered by key words and be able to be parked into a members personal favorite bin etc for future access.

Eg some of Shannow's or Tom NJ's posts can easily be viewed as a "sticky" reference threads for public favorites bin.