Understanding Viscosity and HTHS

[RDY4WAR]

Originally Posted by d00df00d
Originally Posted by Gokhan
Originally Posted by d00df00d
Gokhan, you know better. Stop this.

Stop what? I calculated the viscosity-index improver (VII) content and from that the viscosity and viscosity index (VI) of the base oil.

No, you didn't. You ran the numbers through a series of equations you made up -- equations with zero experimental validation and mostly negative feedback from the few real experts who deigned to comment -- and then you posted the results as though they were completely legit.

If you tried this in a professional or academic setting, any reputable company or institution would laugh you out of the room, and you know it.

There are bloody good reasons for that, and you know it.

So much of what you do here is valuable. So much of what you've posted in this thread and others is on-point and insightful. You can do better. You do it all the time. It's some of the most valuable content on the site. And then you do stuff like this, trying to claim a veneer of legitimacy for something you know hasn't earned it, and it undermines not only your credibility but the whole forum's. And again, you know it.

What you do here matters. You have a much higher standard to uphold than almost everyone else here has. You know how to uphold it. Please make the choice to do so.

Anytime I see his post start mentioning VII content, I stop reading and scroll on past it. I've tested his theory with a few oils that I know the exact VII concentration and it's way off (2% or greater) on all of them.

 

[Gokhan]

Originally Posted by d00df00d
You ran the numbers through a series of equations you made up -- equations with zero experimental validation and mostly negative feedback from the few real experts who deigned to comment -- and then you posted the results as though they were completely legit.

I disagree with you here.

The equations at least work in the case of the oils in the Exxon Mobil blending guide and there were some other checks with a couple of commercial oils. These alone are good checks.

Sure, they are still estimates and there are error bars, but I never claimed 2% accuracy. Of course, they are also relying on the accuracy of the input data (KV40, KV100, HTHSV, and the density).

For example, the base-oil VI values I calculated in this thread are in excellent agreement with the MSDSs for Motul (Group III) and M1 (GTL & PAO).

If we don't calculate or measure anything, then we have really nothing to discuss in this forum other than pure speculation.

Once again, I stand by my calculations for the VII content and base-oil viscosity, with the said caveats. The beauty of the calculations lie in their simplicity. Simple physics based on solid background hardly fails, as there is so little to fail because of the simplicity. Yes, there were some criticisms -- some fair and others unfair -- but they stood firmly and got validated after each one.

 

[Gokhan]

Originally Posted by RDY4WAR
Anytime I see his post start mentioning VII content, I stop reading and scroll on past it. I've tested his theory with a few oils that I know the exact VII concentration and it's way off (2% or greater) on all of them.

OK, what are these oils and how do you know their VII content?

 

[RDY4WAR]

Originally Posted by Gokhan
Originally Posted by RDY4WAR
Anytime I see his post start mentioning VII content, I stop reading and scroll on past it. I've tested his theory with a few oils that I know the exact VII concentration and it's way off (2% or greater) on all of them.

OK, what are these oils and how do you know their VII content?


It's a boutique brand, not common to this board, and I know the VII content because I'm good friends with the man who formulated it. In fact, we're putting together a one-off formula that's being tested this summer. I'll probably post a VOA of it here in the coming months.

 

[Shannow]

Originally Posted by JAG
Quote
Minimum oil film thickness (MOFT) is pretty close to proportional to HTHS, so 0.1/3.5 = 1/35 = about 3% difference in MOFT, not really that much.

I've read multiple papers that said it is proportional to the SQUARE ROOT of the high shear rate viscosity at whatever the temperature of the oil is.


Going back to basics...from experimental evidence...here's the MOFT versus bearing characteristic number for various shaft geometries

It's dimensionless...the bottom being the Somerfeld number (take out the R/C component and you see the bottom axis of the Stribeck curve), L/D is the length.diameter, and the MOFT is relative.

Pick the bottom line L/D=1/4...depends on where you are on the curve how linear/exponential it is....

edit...its from an old thread of mine..

https://www.bobistheoilguy.com/forums/ubbthreads.php/topics/3686791/all/Bearings...how_they_work.

 

[Tom NJ]

Originally Posted by d00df00d
Originally Posted by Gokhan
Originally Posted by d00df00d
Gokhan, you know better. Stop this.

Stop what? I calculated the viscosity-index improver (VII) content and from that the viscosity and viscosity index (VI) of the base oil.

No, you didn't. You ran the numbers through a series of equations you made up -- equations with zero experimental validation and mostly negative feedback from the few real experts who deigned to comment -- and then you posted the results as though they were completely legit.

If you tried this in a professional or academic setting, any reputable company or institution would laugh you out of the room, and you know it.

There are bloody good reasons for that, and you know it.



+1000 Calculating a percent VII (to two decimal places nonetheless) when one doesn't even know which VIIs are being used, or the rest of the formulation that influences the VI and viscosity, and based on published typical viscometrics to boot, is utterly absurd.

 

[Garak]

Originally Posted by Gokhan
The equations at least work in the case of the oils in the Exxon Mobil blending guide and there were some other checks with a couple of commercial oils. These alone are good checks.

Sure, they are still estimates and there are error bars, but I never claimed 2% accuracy. Of course, they are also relying on the accuracy of the input data (KV40, KV100, HTHSV, and the density).

The existence of this "full shear" regime hasn't even yet been demonstrated, but we have a number to describe behaviour within it. That problem still hasn't disappeared; nor has the problem you acknowledged about the input values.

 

[Shannow]

Originally Posted by Garak

The existence of this "full shear" regime hasn't even yet been demonstrated, but we have a number to describe behaviour within it. That problem still hasn't disappeared; nor has the problem you acknowledged about the input values.


Given that the understanding of the second newtonian regime, and that VII still was active in that regime was absent in the intiial presentation of the current discovery, there's no solid foundation for the "science" being portrayed...number mashing isn't science.

 

[OVERKILL]

Originally Posted by Gokhan


M1 FS 0W-40 base-oil viscosity: 2.1 cP
Motul 8100 X-clean EFE 5W-30 base-oil viscosity: 2.2 cP


Is this your calculated at 150C figure? If so, you forgot to include that in your statement.

If we are talking base oil viscosity at 100C, then looking at an example:

The 0w-40 in the Mobil 1 blending guide, which is PAO-based, contains:
- 43.5% SpectraSyn 4
- 23% SpectraSyn 6
- 10% Synesstic 5
- 12% VII

So, we are looking at an AVERAGE base oil viscosity of around 5cSt, and it has roughly double the VII content that you've calculated for the current "FS" product, which also has a higher HTHS and lower KV100, which points to an even thicker base oil blend.

 

[oil_film_movies]

Originally Posted by JAG
Quote
Minimum oil film thickness (MOFT) is pretty close to proportional to HTHS, so 0.1/3.5 = 1/35 = about 3% difference in MOFT, not really that much.
I've read multiple papers that said it is proportional to the SQUARE ROOT of the high shear rate viscosity at whatever the temperature of the oil is.
True, yet you can think of it as linear proportional around any given condition. This is how we explain things for practical application without unnecessarily complicating the issue. This is an oil forum, and not everyone has an engineering degree that reads this stuff.

For example, take a look at the MOFT at the condition circled in red below. Note the micron units of MOFT is actually about the same number as HTHS for the oil tested !
( https://www.bobistheoilguy.com/foru...5484/re-engine-oil-viscosity#Post4415484 )

 

[oil_film_movies]

Originally Posted by Gokhan
As Jim Allen once said, the optimal oil viscosity grade is the thinnest oil that is thick enough (or something to that effect -- I can't remember his exact words).
My take: Find out what the required HTHSV is for your car and don't go any higher. Then, find an oil that with the least viscosity-index improver (VII) content that meets this HTHSV spec. This will result in the highest fuel economy, smoothest- and cleanest-running engine, and probably the least engine wear as well.

I've been recommending never adding about +0.5 HTHS over the lowest recommended by the engine maker.

Your paper you cited above blames partial oil starvation (lower flow) of the extremely high HTHS oils for the gradual increase in wear as HTHS goes up excessively. ----> Take an HTHS 2.7 (0w20) oil recommendation for example: You can easily use HTHS 3.2 in that engine and you will get slightly better wear performance. (Even HTHS 3.5 probably on the higher end.) Much higher than that and you may encounter the starvation issues as the engineer saw on the rod big end. (see https://www.bobistheoilguy.com/foru...rstanding-viscosity-and-hths#Post5110672 for the citation )

 

[oil_film_movies]

Originally Posted by Shannow
Going back to basics...from experimental evidence...here's the MOFT versus bearing characteristic number for various shaft geometries.

 

[JustN89]

Originally Posted by Garak
Originally Posted by JustN89
My cars spec 5W-20, 5W-30 and 10W-30, and I've been running 5W-30 in both for the majority of the time I've owned them. They're both port injected, naturally aspirated, and seem relatively easy on oil. Anyways, I started looking at different 5W-30 oils and got to wondering something.

You mention warranty concerns, so I thought I should bring up something in the regard. And no, it's not about whether using the wrong viscosity will or won't void your warranty, either. I'll leave that one alone.

Note that when a manual specifies one or more viscosities, they usually specify something else along with viscosity, such as API, ILSAC, ACEA, or proprietary specifications. You mentioned API, but most will specify something else. My G37 specifies only 5w-30 in API (SM was current then). ILSAC was only optional. A dexos2/SN 5w-30 or a CK-4/SN 5w-30 perfectly meet my [expired] warranty requirements, but that's not the case for everyone.

When it comes to your italicized question, that's been creating debate here for a very long time. The difference in HTHS between the 5w-30 CK-4 I'm running and an A3/B4 or C3 0w-40 is much closer than the difference between my 5w-30 and an ILSAC 5w-30.

Thanks for the input!

I'm not really concerned with running either of these oils in my car nor about the warranty. I think my original intent was misunderstood and that's my fault for not asking the right questions or wording them clearly. However, I'll just say that the reason I brought up my engine is because Hyundai is notoriously vague with oil requirements and my OM states that the use of "API SM, ILSAC GF-4 (or above) and ACEA A5 (or above)" is required. This gives me a lot of freedom to run different oils and I just started to contemplate viscosities and figured I'd ask my original question.

 

[LEADED]

That's fine for virgin PCMO , I am more interested in what a PCMO comes out after say 7K miles run in a turbo engine . I leave Formulating PCMO to the TRIBOS .

 

[oil_film_movies]

Originally Posted by LEADED
That's fine for virgin PCMO , I am more interested in what a PCMO comes out after say 7K miles run in a turbo engine . I leave Formulating PCMO to the TRIBOS .
Then leave turbo performance to those "TRIBOS" and their swanky General Motors Turbocharger Coking (GMTC) Test in dexos1 Gen2 oils:
https://www.sae.org/publications/technical-papers/content/2017-01-2341/

Choose dexos1 oils for turbo performance. Amsoil SS & the upcoming Mobil1 Turbo oil claim to score exceptionally well on that new GMTC amongst dexos1 oils though.

"A couple decades ago the technology suffered quality issues, most notably a "coking" up of small bearings inside the turbo causing a loss of viscosity and leading to failures. New designs control heat better to eliminate coking." -- https://www.wardsauto.com/technology/gm-debunks-turbocharger-myths

 

[d00df00d]

Originally Posted by JustN89
I'm not really concerned with running either of these oils in my car nor about the warranty. I think my original intent was misunderstood and that's my fault for not asking the right questions or wording them clearly. However, I'll just say that the reason I brought up my engine is because Hyundai is notoriously vague with oil requirements and my OM states that the use of "API SM, ILSAC GF-4 (or above) and ACEA A5 (or above)" is required. This gives me a lot of freedom to run different oils and I just started to contemplate viscosities and figured I'd ask my original question.

FWIW, X-Clean EFE is not at all a GF-4 or A5 oil.

 

[JustN89]

Originally Posted by d00df00d
Originally Posted by JustN89
I'm not really concerned with running either of these oils in my car nor about the warranty. I think my original intent was misunderstood and that's my fault for not asking the right questions or wording them clearly. However, I'll just say that the reason I brought up my engine is because Hyundai is notoriously vague with oil requirements and my OM states that the use of "API SM, ILSAC GF-4 (or above) and ACEA A5 (or above)" is required. This gives me a lot of freedom to run different oils and I just started to contemplate viscosities and figured I'd ask my original question.

FWIW, X-Clean EFE is not at all a GF-4 or A5 oil.

And Quaker State isn't either, yet that's the recommended oil.

 

[d00df00d]

Originally Posted by JustN89
Originally Posted by d00df00d
Originally Posted by JustN89
I'm not really concerned with running either of these oils in my car nor about the warranty. I think my original intent was misunderstood and that's my fault for not asking the right questions or wording them clearly. However, I'll just say that the reason I brought up my engine is because Hyundai is notoriously vague with oil requirements and my OM states that the use of "API SM, ILSAC GF-4 (or above) and ACEA A5 (or above)" is required. This gives me a lot of freedom to run different oils and I just started to contemplate viscosities and figured I'd ask my original question.

FWIW, X-Clean EFE is not at all a GF-4 or A5 oil.

And Quaker State isn't either, yet that's the recommended oil.

Seriously?

Which Quaker State oil?

 

[Gokhan]

Originally Posted by RDY4WAR
It's a boutique brand, not common to this board, and I know the VII content because I'm good friends with the man who formulated it. In fact, we're putting together a one-off formula that's being tested this summer. I'll probably post a VOA of it here in the coming months.

The formula only works with the OCP VII. If it's a different type of VII, you need to use different constants for the VII viscosity-boost rate and VII temporary-shear rate. Most commercial oils use OCP VII these days because they have a hard time passing the industry and OEM tests for the engine and turbocharger deposits otherwise, but since boutique oils don't get tested and certified, they tend to use random additives.

 

[Gokhan]

Originally Posted by OVERKILL
Originally Posted by Gokhan


M1 FS 0W-40 base-oil viscosity: 2.1 cP
Motul 8100 X-clean EFE 5W-30 base-oil viscosity: 2.2 cP


Is this your calculated at 150C figure? If so, you forgot to include that in your statement.

If we are talking base oil viscosity at 100C, then looking at an example:

The 0w-40 in the Mobil 1 blending guide, which is PAO-based, contains:
- 43.5% SpectraSyn 4
- 23% SpectraSyn 6
- 10% Synesstic 5
- 12% VII

So, we are looking at an AVERAGE base oil viscosity of around 5cSt, and it has roughly double the VII content that you've calculated for the current "FS" product, which also has a higher HTHS and lower KV100, which points to an even thicker base oil blend.

Of course, it's the dynamic base-oil viscosity at 150 C.

You can't make any oil out of a base oil with a kinematic viscosity KV100 = 2 cSt. The Noack would be something like 40%.