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Re: Understanding Viscosity and HTHS [Re: Gokhan] #5111006 05/21/19 08:25 AM
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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 )

Re: Understanding Viscosity and HTHS [Re: Shannow] #5111008 05/21/19 08:26 AM
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Originally Posted by Shannow
Going back to basics...from experimental evidence...here's the MOFT versus bearing characteristic number for various shaft geometries.

[Linked Image]

Re: Understanding Viscosity and HTHS [Re: Garak] #5111014 05/21/19 08:29 AM
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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. wink

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.

Re: Understanding Viscosity and HTHS [Re: JustN89] #5111060 05/21/19 09:15 AM
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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 .

Re: Understanding Viscosity and HTHS [Re: LEADED] #5111089 05/21/19 09:37 AM
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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

Re: Understanding Viscosity and HTHS [Re: JustN89] #5111201 05/21/19 11:20 AM
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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.


2008 BMW M3 Sedan 6MT
Re: Understanding Viscosity and HTHS [Re: d00df00d] #5111221 05/21/19 11:47 AM
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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.

Re: Understanding Viscosity and HTHS [Re: JustN89] #5111269 05/21/19 12:29 PM
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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?


2008 BMW M3 Sedan 6MT
Re: Understanding Viscosity and HTHS [Re: RDY4WAR] #5111280 05/21/19 12:40 PM
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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.


2020 Toyota Prius Prime XLE plug-in hybrid, 2ZR-FXE engine, ~ 70 mpg on gas, ~ 5,000 mi
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Re: Understanding Viscosity and HTHS [Re: OVERKILL] #5111284 05/21/19 12:47 PM
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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%.


2020 Toyota Prius Prime XLE plug-in hybrid, 2ZR-FXE engine, ~ 70 mpg on gas, ~ 5,000 mi
TGMO 0W-16 SN/RC Japan
OEM spin-on oil filter Japan
Re: Understanding Viscosity and HTHS [Re: d00df00d] #5111290 05/21/19 12:54 PM
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JustN89 Offline OP
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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.

Last edited by JustN89; 05/21/19 12:55 PM. Reason: deleting some previously quoted remarks
Re: Understanding Viscosity and HTHS [Re: Gokhan] #5111292 05/21/19 12:56 PM
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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.


2019 RAM 1500 Sport - Mobil 1 EP 0w-20, FRAM Ultra
2020 Grand Cherokee SRT - Ravenol SSL 0w-40, FRAM Ultra
Re: Understanding Viscosity and HTHS [Re: JustN89] #5111338 05/21/19 01:42 PM
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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.

[Linked Image]

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.


2020 Toyota Prius Prime XLE plug-in hybrid, 2ZR-FXE engine, ~ 70 mpg on gas, ~ 5,000 mi
TGMO 0W-16 SN/RC Japan
OEM spin-on oil filter Japan
Re: Understanding Viscosity and HTHS [Re: Gokhan] #5111429 05/21/19 03:12 PM
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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:

[Linked Image]

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.

Re: Understanding Viscosity and HTHS [Re: oil_film_movies] #5111473 05/21/19 03:52 PM
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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.

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