Viscosity @ 40°C a predictor of Cold Pumpability?

[Drew7a]

Is the 40°C viscosity value of an oil indicative of what it pumpability will be in extreme cold temperatures?

Take 4 different oils to be nameless for now but from the majors all 30 grade,

Oil #1 has a KV @ 40°C of 66.4cSt and at 100°C 11.7cSt
Oil #2 has a KV @ 40°C of 66cSt and at 100°C 10.4cSt
Oil #3 has a KV @ 40°C of 61cSt and at 100°C 10.5cSt
Oil# 4 has a KV @ 40°C of 62.3cSt and at 100°C 10.4cSt

Just by these numbers and not looking at the Winter rating is it even possible to extrapolate which will pump the best at the lower temperatures?
I know viscosity is not linear and more exponential as you get colder. but given they are all roughly at the same point on the graph wont they all pump the same?

 

[SuperSalad]

No, the 40°C viscosity is no indicative of the subzero viscosity. You could attempt to extrapolate and maybe get an accurate result, but it could just as easily be inaccurate. Two points are not enough to create a reliably accurate trend line for this property since there are multiple factors that can affect all three of those viscosity to temperature relationships.

 

[kschachn]

Well as one data point, the reason SAE J300 was revised IRT the winter rating was because none of the tests at the time accurately predicted the behavior of the oil at very low temperatures. What results in the winter rating today is a far better representation.

ASTM D5293 and D4684 specifically address the behavior of the oil at very low temperatures, why try and substitute something else? What would be the point in doing so and what additional and previously unobtainable information would be obtained?

 

[Drew7a]

Well as one data point, the reason SAE J300 was revised IRT the winter rating was because none of the tests at the time accurately predicted the behavior of the oil at very low temperatures. What results in the winter rating today is a far better representation.

ASTM D5293 and D4684 specifically address the behavior of the oil at very low temperatures, why try and substitute something else? What would be the point in doing so and what additional and previously unobtainable information would be obtained?

After posting this I came across the widman calculator he seems to use two data points to extrapolate? Are those numbers flawed?

Also most manufacturers seems to pick an choose what number to present and only list that make their products seems better and not list other numbers. one examples come to mind not picking on Mobile but (M1 0w-40 touts is -60° pour point but not is -35°C dynamic Viscosity, but on its 5w-30EP it will not list the KV @ 40°C but lists its dynamic viscosity).

BTW Oil # 2 was a 10w30 M1 HM and it looked liked it was behaving like a 5w-30

 

[kschachn]

After posting this I came across the widman calculator he seems to use two data points to extrapolate? Are those numbers flawed?

Also most manufacturers seems to pick an choose what number to present and only list that make their products seems better and not list other numbers. one examples come to mind not picking on Mobile but (M1 0w-40 touts is -60° pour point but not is -35°C dynamic Viscosity, but on its 5w-30EP it will not list the KV @ 40°C but lists its dynamic viscosity).

BTW Oil # 2 was a 10w30 M1 HM and it looked liked it was behaving like a 5w-30

What does the Widman calculator say for accuracy at low temperatures?

And if an oil behaves as one with a 10W rating then it is labeled as such. If it behaves as one with a 5W rating then it is labeled as a 5W. Your mention of pour point is the prime example of the problem that was seen with predicting behavior at low temperatures. The only thing that ExxonMobil "touts" in regards to cold weather performance is the winter rating.

What is published as the winter rating is an accurate performance the oil achieves. Are you suggesting you know a method that is a better predictor of the low temperature behavior of motor oil than the tests in SAE J300?

 

[kschachn]

I think that user has this reply saved somewhere so it can be used as a cut-and-paste.

 

[slybunda]

Would be good if they gave a 10c cst rating on oils. Good idea of average cold start flowability

 

[SuperSalad]

Or maybe.....bear with me here, they could make some sort of official cold weather rating, let's just call it a winter rating and be abbreviated with a number and the letter "W" for easy labelling. Ok, so hear me out now. It could go from 0 to 25 in increments of 5, with "0W" being the easiest to pump/flow at low temperature and "25W" being the most difficult to pump/flow at low temperature. We could designate two very good lab tests that are remarkably good at predicting real world conditions for pumpability and flow and base the ratings on those. Then those ratings could easily differentiate between significant differences and consumers wouldn't need to worry about the minutia of inconsequential differences.

You know, now that I say it out loud, it sounds ridiculous, forget I said anything.

 

[kschachn]

Would be good if they gave a 10c cst rating on oils. Good idea of average cold start flowability

Except that in a very limited sense flow doesn’t matter, does it?

 

[wpod]

40c is 104 Degrees F. not cold. The W part of the 5W-30 is the cold rating. are you trying to extrapolate the pumpability down to some starting temp?

 

[OVERKILL]

Is the 40°C viscosity value of an oil indicative of what it pumpability will be in extreme cold temperatures?

No. A 0w-20 can have a lower VI than a 5w-30 and will absolutely kick the crap out of it in the MRV pumpability test.

A 0w-40 will have a much higher KV40 than an SAE 20, but will be pumpable long after the SAE 20 is solid.

For example,
AEGIS SAE 20 specs:
100C: 8.5cSt
40C: 68cSt
Pour Point: -26C

Ravenol 0w-40 specs:
100C: 13.25cSt
40C: 74.4cSt
Pour Point: -60C

 

[ZeeOSix]

No, the 40°C viscosity is no indicative of the subzero viscosity. You could attempt to extrapolate and maybe get an accurate result, but it could just as easily be inaccurate. Two points are not enough to create a reliably accurate trend line for this property since there are multiple factors that can affect all three of those viscosity to temperature relationships.

And probably why 40C is the lowest temp that a KV is typically specified/given in a data sheet. Once the temperature goes below that, as mentioned the viscosity can go off track of the viscosity vs temperature curve (like the Widman calculator shows) depending on the formulation.

 

[Drew7a]

I think we got derailed a bit here and let me rephrase. Lets say you have oils with all the same "W" rating for argument sake lets say it is a 5W. How does one determine which from a given set of oils with a 5W will pump the easiest at extreme cold temperatures. I'm sure there is a range in which they would fall within the 5W rating. For operating viscosity, I have seen it posted lots time people referring to it as thin 30 or a thick 30 even though they are all within grade, but one is less viscous than the other. For the W rating we don't really know as most of the time the MRV pumpability results are not posted. So I was just wondering if that could be extrapolated based on what is given by the manufacturers hence the question about the KV40

Yes in practicality a 5W is a 5w and will work at the specified temperature but that is not the point of my question.

 

[ZeeOSix]

I think we got derailed a bit here and let me rephrase. Lets say you have oils with all the same "W" rating for argument sake lets say it is a 5W. How does one determine which from a given set of oils with a 5W will pump the easiest at extreme cold temperatures. I'm sure there is a range in which they would fall within the 5W rating. For operating viscosity, I have seen it posted lots time people referring to it as thin 30 or a thick 30 even though they are all within grade, but one is less viscous than the other. For the W rating we don't really know as most of the time the MRV pumpability results are not posted. So I was just wondering if that could be extrapolated based on what is given by the manufacturers hence the question about the KV40

Yes in practicality a 5W is a 5w and will work at the specified temperature but that is not the point of my question.

SAE J300 defines the W ratings cut-off crankng and pumping viscosity at defined temperatures. What a specific oil comes in at will never be given by the oil manufacture ... all they will do is give it a W rating. There's essentially only a 5 deg C range between each W category for the low temp pumping rating.

 

[Drew7a]

40c is 104 Degrees F. not cold. The W part of the 5W-30 is the cold rating. are you trying to extrapolate the pumpability down to some starting temp?

Yes that is what I am trying to do to see which is the easiest to pump at a given low temp from a sample of oils with the same W rating.

Some people here obsess over a 3cSt operating spread for a 30 grade, but don't seem to care too much about 100's of cST spread at extreme cold temps as long as it had the proper "W" rating because the manufacturer said it has a given rating and is rated to pump at a given temp. So the inverse of that would be, why care if its a 9.5cST 30 or a 12Cst 30? Hey that same manufacturer said it performs as a 30 grade why care?

 

[Drew7a]

SAE J300 defines the W ratings cut-off crankng and pumping viscosity at defined temperatures. What a specific oil comes in at will never be given by the oil manufacture ... all they will do is give it a W rating.

View attachment 67753

Thanks I have seen those charts. So I guess that is the answer is the manufacturers will not give that number as long as it pumps in that given range it is given that rating.

 

[ZeeOSix]

Yes that is what I am trying to do to see which is the easiest to pump at a given low temp from a sample of oils with the same W rating.

You will never know unless you do the official cold cranking and pumpability tests on specific oils.

If you're super worried about cold pumpability, then use a 0W.

 

[kschachn]

You will never know unless you do the official cold cranking and pumpability tests on specific oils.

If you're super worried about cold pumpability, then use a 0W.

Plus pumpability is more of a binary than a range of values. Either it pumps or it does not and that's what the rating is really about.

 

[ka9mnx]

Huh. The lower the xW the lower it will pump. Who would have thunk it?

 

[kschachn]

Yes that is what I am trying to do to see which is the easiest to pump at a given low temp from a sample of oils with the same W rating.

Some people here obsess over a 3cSt operating spread for a 30 grade, but don't seem to care too much about 100's of cST spread at extreme cold temps as long as it had the proper "W" rating because the manufacturer said it has a given rating and is rated to pump at a given temp. So the inverse of that would be, why care if its a 9.5cST 30 or a 12Cst 30? Hey that same manufacturer said it performs as a 30 grade why care?

That's because the operating viscosity is a long-term value in operation whereas the cold pumping loss is transient and temporary. As I noted above what matters is whether the oil will pump or whether it will gel in the vicinity of the pickup tube due to shear. If it pumps (which the winter rating is designed over) then the oil will warm up in short order. People "don't seem to care too much" about the cold cranking differences because in the scheme of things it's not important as long as the oil will pump. If it doesn't pump then game over.