Understanding Viscosity and HTHS

[JustN89]

Originally Posted by d00df00d
Originally Posted by JustN89
Originally Posted by d00df00d
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?

Any of them, I think. Both Advanced and Ultimate are API SN Plus, GF-5 and no ACEA approval. However, Quaker State is what is recommended on the air filter box and in the OM.

 

[OVERKILL]

Originally Posted by 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%.


I know that, but you didn't spell it out, and you needed to. Remember your audience.

 

[Gokhan]

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.

The Hyundai/Kia recommended oil is an oil with an HTHSV ~ 3.0 cP (ACEA A5/B5 or C2). Now, it's true that many C2 oils have HTHSV = 3.5 cP but that doesn't change the fact that down to 2.9 cP is allowed for C2. I am guessing for your particular engine it's A5/B5.

In US, for all practical purposes, ACEA A5/B5 = GM dexos1. In fact, it's also OK to use dexos1 when C2 is recommended.

There is no need to overthink this. Pick any dexos1 5W-30. I would probably use the Pennzoil Platinum 5W-30 because it has very little VII but any oil with dexos1 is OK.

You can ignore the thicker oils in the oil chart. Nothing above 5W-30 (except 10W-30) will fall into A5/B5 or C2. They are not the recommended oils -- they are alternative oils for countries or locations where the recommended oils are not available or the laws (such as in Europe) prevent the manufacturers from making too strict oil recommendations or for anyone who wants to have more freedom of choice when putting oil.

 

[ZeeOSix]

Originally Posted by Gokhan
This is the dependence of the bearing wear on HTHSV and MOFT, the latter being proportional to the square root of the HTHSV:

Contrary to what one might naïvely expect, the bearing wear actually increases with the increasing HTHSV and increasing MOFT. My guess for the reason for this phenomenon is that the increasing HTHSV increases the bearing temperature, which in turn increases the bearing corrosion and wear. Nevertheless, there is a minimum HTHSV that is needed below which catastrophic bearing failure occurs.


Based on that data, you don't want to be operating with no headroom in the MOFT just to try and squeak out a hair less wear as a trade-off for catastrophic failure at the point where the wear line shoots straight up.

 

[ZeeOSix]

Originally Posted by 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 )


To add ... I'm not so sure I totally buy into the "oil starvation" statement as a function of oil viscosity made in that paper. As shown by the table posted earlier, journal bearings flow much more oil as their RPM increases (even though flow is reduced by higher viscosity at a constant RPM), and that along with the forced lubrication (positive displacement oil pump) I can't really believe bearings would be oil starved enough to cause damage just because a higher viscosity was used. Sure there is more heat produced from shearing at higher RPM and from the higher viscosity, but the MOFT is also increased, which helps to ensure no metal-to-metal contact. That is the basic reason why manufactures of high performance engines recommend higher viscosity oil for track use to protect the engine better. Even though the oil heats up more in the sump and in the bearings with extreme use, the MOFT is still increased for added protection (less wear).

Wear only occurs in journal bearings when there is metal-to-metal contact, and if the MOFT is always preventing parts from rubbing on each other then there is no wear. IMO, the only way that thicker oil could cause more wear is if the heating of the oil inside the bearing was so great that the MOFT went to zero and metal-to-metal contact occurs. Too tight of bearing clearances (which cuts flow, heats the oil more and reduces MOFT), and inadequate PD oil pump performance has more to do with oil starvation of oil flow through the bearings than solely the viscosity used.

 

[Shannow]

Originally Posted by 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.

Note what I said, and the curve that I posted...your line doesn't go to zero, nor another 2 orders of magnitude to the right...small sections of a curve look just like a....line...

 

[Gokhan]

Originally Posted by ZeeOSix
Originally Posted by 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 )
To add ... I'm not so sure I totally buy into the "oil starvation" statement as a function of oil viscosity made in that paper. As shown by the table posted earlier, journal bearings flow much more oil as their RPM increases (even though flow is reduced by higher viscosity at a constant RPM), and that along with the forced lubrication (positive displacement oil pump) I can't really believe bearings would be oil starved enough to cause damage just because a higher viscosity was used. Sure there is more heat produced from shearing at higher RPM and from the higher viscosity, but the MOFT is also increased, which helps to ensure no metal-to-metal contact. That is the basic reason why manufactures of high performance engines recommend higher viscosity oil for track use to protect the engine better. Even though the oil heats up more in the sump and in the bearings with extreme use, the MOFT is still increased for added protection (less wear).

Wear only occurs in journal bearings when there is metal-to-metal contact, and if the MOFT is always preventing parts from rubbing on each other then there is no wear. IMO, the only way that thicker oil could cause more wear is if the heating of the oil inside the bearing was so great that the MOFT went to zero and metal-to-metal contact occurs. Too tight of bearing clearances (which cuts flow, heats the oil more and reduces MOFT), and inadequate PD oil pump performance has more to do with oil starvation of oil flow through the bearings than solely the viscosity used.

I don't buy the oil-starvation hypothesis either -- although it could happen in certain conditions when the viscosity is too high.

There are two factors that determine the bearing wear and you don't seem to know about the latter, which is I think the dominating factor in most engines: (1) contact, either directly or through particles or through surface imperfections and (2) corrosion.

Detergents and antioxidants protect against the corrosion and certain additives and base oils increase corrosion. Another thing that obviously increases the corrosion is the bearing temperature and obviously the bearing temperature increases with the increasing HTHSV, as the hydrodynamic friction increases. Therefore, I think the increase in the bearing wear with the increasing HTHSV is because of the increasing bearing temperature accelerating the corrosion. Most modern engine bearings seem to run just fine with 0W-20 with no noticeable wear and the corrosion seems to be the main factor causing the bearing wear. That's another reason to stick with the manufacturer's oil-change intervals so that you don't have the build-up of acids.

 

[Gokhan]

Originally Posted by JustN89
Originally Posted by d00df00d
Originally Posted by JustN89
Originally Posted by d00df00d
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?

Any of them, I think. Both Advanced and Ultimate are API SN Plus, GF-5 and no ACEA approval. However, Quaker State is what is recommended on the air filter box and in the OM.

Now, let's dwell into the Quaker State question.

Quaker State Ultimate Durability and its more expensive sibling Pennzoil Platinum have entirely different viscosity characteristics.

Pennzoil Platinum:

KV40 = 53.9
KV100 = 9.8
VI = 170
density = 0.839

Quaker State Ultimate Durability:

KV40 = 66.65
KV100 = 11.60
VI = 170
density = 0.837

I have run my calculator assuming olefin copolymer (OCP) VII and adjusted the HTHSV until the base-oil viscosity index (VI) made sense. This is what I got:

Pennzoil Platinum:

HTHSV = 3.0 cP
VII content: 3.8%
dynamic base-oil viscosity at 150 C: 2.1 cP
base-oil viscosity index: 135 (adjusted to be GTL)


Quaker State Ultimate Durability 5W-30:

HTHSV = 3.3 cP
VII content: 6.0%
dynamic base-oil viscosity at 150 C: 2.1 cP
base-oil viscosity index: 126 (adjusted to be Group III+)

Therefore, Quaker State Ultimate Durability is an exceptional 5W-30. With HTHSV = 3.3 cP, it's probably the thickest non-Euro 5W-30 you can find. It looks like Hyundai/Kia are not joking when they are recommending Quaker State. Use it if you want an exceptionally thick ILSAC 5W-30. The other option will be an ACEA C2 & C3 5W-30 with HTHSV = 3.5 cP. Most ILSAC 5W-30 oils have HTHSV = 3.0 - 3.1 cP.

Some people expressed doubts about my calculator, which I understand, but the more I use it, I appreciate what a powerful calculator it is. If you can determine the HTHSV of an oil using it, this is indeed remarkable!

 

[ZeeOSix]

Originally Posted by Gokhan
There are two factors that determine the bearing wear and you don't seem to know about the latter, which is I think the dominating factor in most engines: (1) contact, either directly or through particles or through surface imperfections and (2) corrosion.


I was addressing the specific comments made in the paper about "increased wear with increased MOFT". That kind of seems like an oxymoron statement because in terms of the oil viscosity and HTSH factor only (not corrosion factors which the paper doesn't seem address), the MOFT in hydrodynamic lubrication is what's preventing metal-to-metal contact. If the MOFT goes up with increased viscosity, and if wear is increased with the decrease and breakdown of MOFT, then how can wear increase solely from the increased viscosity factor. Maybe there is increased oil cavitation as the viscoity increases and that's what is actually causing more bearing wear as the viscoity increases - ?? Maybe something else to ponder.

 

[Gokhan]

Originally Posted by ZeeOSix
Originally Posted by Gokhan
There are two factors that determine the bearing wear and you don't seem to know about the latter, which is I think the dominating factor in most engines: (1) contact, either directly or through particles or through surface imperfections and (2) corrosion.
I was addressing the specific comments made in the paper about "increased wear with increased MOFT". That kind of seems like an oxymoron statement because in terms of the oil viscosity and HTSH factor only (not corrosion factors which the paper doesn't seem address), the MOFT in hydrodynamic lubrication is what's preventing metal-to-metal contact. If the MOFT goes up with increased viscosity, and if wear is increased with the decrease and breakdown of MOFT, then how can wear increase solely from the increased viscosity factor. Maybe there is increased oil cavitation as the viscoity increases and that's what is actually causing more bearing wear as the viscoity increases - ?? Maybe something else to ponder.

Well, as I said, increasing the MOFT increases the hydrodynamic friction, which increases the bearing temperature, which in turn accelerates the corrosion of lead and copper, which accelerates the wear of these bearing metals.

Yes, the authors didn't comment on corrosion-induced wear. Perhaps, they didn't know about it. But that's my take. A major source of wear for chromium, copper, and lead in engines is corrosion:

https://www.jstor.org/stable/44469140

"Corrosive wear is the silent diesel-engine killer."

Mechanism of wear control by the lubricant in diesel engines
J. A. McGeehan and A. V. Kulkarni
Chevron Research Company, Richmond, California
SAE Transactions, Vol. 96, Section 7: Fuels and Lubricants (1987), pp. 202-215

http://www.oil-lab.com/downloads/TBN-1.pdf

TBN Retention -- Are we missing the point? Diesel-engine lubricant characterization using multiple used-oil analyses
W. van Dam, D. H. Broderick, R. L. Freerks, V. R. Small, and W. W. Willis
Oronite Global Technology

 

[Garak]

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.

It's hard to word the question clearly when the specification wording isn't clear.

The G37's spec is actually written very well, despite being fairly open all the while technically calling for one viscosity and a fairly short severe service OCI. So, ordinary SM/GF-4 or newer was acceptable as was any SM or newer 5w-30 including C3 or E6 or A1/B1 or A5/B5, as long as an SM or newer API category was there along with the 5w-30 viscosity. I went out of viscosity spec in any event to a 5w-40 CJ-4/SM E7, E9.

 

[oil_film_movies]

Originally Posted by Gokhan

Quaker State Ultimate Durability 5W-30:
HTHSV = 3.3 cP
VII content: 6.0%
dynamic base-oil viscosity at 150 C: 2.1 cP
base-oil viscosity index: 126 (adjusted to be Group III+)

Therefore, Quaker State Ultimate Durability is an exceptional 5W-30. With HTHSV = 3.3 cP, it's probably the thickest non-Euro 5W-30 you can find. It looks like Hyundai/Kia are not joking when they are recommending Quaker State. Use it if you want an exceptionally thick ILSAC 5W-30.[/color] The other option will be an ACEA C2 & C3 5W-30 with HTHSV = 3.5 cP. Most ILSAC 5W-30 oils have HTHSV = 3.0 - 3.1 cP.

Some people expressed doubts about my calculator, which I understand, but the more I use it, I appreciate what a powerful calculator it is. If you can determine the HTHSV of an oil using it, this is indeed remarkable!


On another thread, we noted there are seveal 5w30 SN GF-5 dexos1 oils that have HTHS 3.3: Schaeffers, Amsoils XL & OE, and if your estimate is correct, QSUD. I've never seen Shell tell us what it is.

 

[d00df00d]

Originally Posted by JustN89
Originally Posted by d00df00d
Originally Posted by JustN89
Originally Posted by d00df00d
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?

Any of them, I think. Both Advanced and Ultimate are API SN Plus, GF-5 and no ACEA approval. However, Quaker State is what is recommended on the air filter box and in the OM.

What's the exact wording in the OM? Could it be saying you can use SN/GF-4 or ACEA A5, depending on what's available?

 

[Gokhan]

Originally Posted by oil_film_movies
On another thread, we noted there are seveal 5w30 SN GF-5 dexos1 oils that have HTHS 3.3: Schaeffers, Amsoils XL & OE, and if your estimate is correct, QSUD. I've never seen Shell tell us what it is.

With the KV100 = 11.60 cSt spec for the Quaker State Ultimate Durability 5W-30 SN PLUS, my HTHSV = 3.3 cP estimate from my VII calculator sounds about right, doesn't it?

Unlike the three other oils you mentioned, you can get it easily everywhere, including at Walmart for only $19.97 + tax for the 5 qt jug.

 

[OilUzer]

Originally Posted by Gokhan
... Some people expressed doubts about my calculator, which I understand, but the more I use it, I appreciate what a powerful calculator it is. If you can determine the HTHSV of an oil using it, this is indeed remarkable!


Speaking of powerful calculators, i have 3 old HP calculators (RPN type) and they are the best. i used to program them to solve all sorts of equations ...

 

[JustN89]

Originally Posted by d00df00d
Originally Posted by JustN89
Originally Posted by d00df00d
Originally Posted by JustN89
"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?

Any of them, I think. Both Advanced and Ultimate are API SN Plus, GF-5 and no ACEA approval. However, Quaker State is what is recommended on the air filter box and in the OM.

What's the exact wording in the OM? Could it be saying you can use SN/GF-4 or ACEA A5, depending on what's available?

It's exactly as I typed it.

 

[d00df00d]

Originally Posted by JustN89
Originally Posted by d00df00d
What's the exact wording in the OM? Could it be saying you can use SN/GF-4 or ACEA A5, depending on what's available?

It's exactly as I typed it.

Yeah, that 100% looks like they're saying you can either use an oil with SM and GF-4 or an oil with ACEA A5 -- not that you have to have all three. Makes sense; ACEA A5 is basically the closest European spec to API SM/SN + ILSAC GF-4/GF-5.

What do those footnotes say?

 

[JustN89]

Originally Posted by d00df00d
Originally Posted by JustN89
Originally Posted by d00df00d
What's the exact wording in the OM? Could it be saying you can use SN/GF-4 or ACEA A5, depending on what's available?

It's exactly as I typed it.

Yeah, that 100% looks like they're saying you can either use an oil with SM and GF-4 or an oil with ACEA A5 -- not that you have to have all three. Makes sense; ACEA A5 is basically the closest European spec to API SM/SN + ILSAC GF-4/GF-5.

What do those footnotes say?

I'm not debating that it's and/or, what I'm saying is that the oil that they recommend doesn't meet what they require which is either API SM AND GF-4 or above (QSUD is GF-5) AND/OR ACEA A5 or above (QSUD does not have an ACEA rating). Not that I'm saying you can't run the oil (it's in my engine now), but just pointing out that Hyundai is very, very vague about what oil is required.

Footnotes:

 

[d00df00d]

Originally Posted by JustN89
Originally Posted by d00df00d
Originally Posted by JustN89
Originally Posted by d00df00d
What's the exact wording in the OM? Could it be saying you can use SN/GF-4 or ACEA A5, depending on what's available?

It's exactly as I typed it.

Yeah, that 100% looks like they're saying you can either use an oil with SM and GF-4 or an oil with ACEA A5 -- not that you have to have all three. Makes sense; ACEA A5 is basically the closest European spec to API SM/SN + ILSAC GF-4/GF-5.

What do those footnotes say?

I'm not debating that it's and/or, what I'm saying is that the oil that they recommend doesn't meet what they require which is either API SM AND GF-4 or above (QSUD is GF-5) AND/OR ACEA A5 or above (QSUD does not have an ACEA rating). Not that I'm saying you can't run the oil (it's in my engine now), but just pointing out that Hyundai is very, very vague about what oil is required.

Footnotes:

Ah, okay. Thanks for clarifying.

ILSAC GF-4 is just API SM plus some other stuff tacked on. Same relationship between ILSAC GF-5 and API SN.

Also, ILSAC and API specs are meant to be backward-compatible. That means a GF-5 oil also meets GF-4, an SN Plus oil also meets SN and therefore SM, etc.

So, if you see a GF-5 oil, that means it also meets GF-4, SN, SM, etc. That means QSUD 5W-30 easily covers the SM + GF-4 requirement in your OM, so there's no contradiction between their spec requirements and their brand recommendation.

As to the "vagueness", maybe I'm misunderstanding your point (again), but I think what you're really seeing is that Hyundai intends for the engine to tolerate a wide variety of oils meeting very common specs. So, it's not that Hyundai is being obscure or noncommittal or anything; it's that they really do think (probably with good reason) that the engine doesn't care what oil you run as long as it's in the right ballpark. Makes sense for a mass-market engine meant to have easy maintenance around the world.

Does that help?

 

[Virtus_Probi]

Originally Posted by OilUzer
Originally Posted by Gokhan
... Some people expressed doubts about my calculator, which I understand, but the more I use it, I appreciate what a powerful calculator it is. If you can determine the HTHSV of an oil using it, this is indeed remarkable!

Speaking of powerful calculators, i have 3 old HP calculators (RPN type) and they are the best. i used to program them to solve all sorts of equations ...

Still use my HP15C from 1983...lost the programming manual years ago and don't remember how to do it anymore, though. There are better tools on a PC for that, anyway.
I think that calc has only used 3-5 sets of batteries in all those years...