Does SAE grade even matter or is it HTHS alone?

[fdcg27]

I've been pondering what oils might be suitable for the needs of my old four cylinder BMW.
I'm coming to the view that the temp/visc chart in the OM is relevant only at the W end of the scale for the operating temperatures expected and that the top end is eclipsed by HTHS.
The only thing that should matter is the minimum required HTHS viscosity, which appears to be 3.5 based upon later BMW oil recommendations or the A3/B3 standard upon which they were originally based.
If this is the case, it opens up a number of grades for all weather use that the temp/visc chart would not allow for warm summer temperatures, like any 10W-30 HDEO or oils like M1 HM 10W-30.
It would also mean that if my '12 Accord is happy on a 0W-20, it should be equally happy on a 0W-16.
Am I missing something here, or is HTHS viscosity more significant than kinematic viscosity in determining the suitability of any given oil to use in any give application?

 

[Shannow]

If I had control, it would be XW-HTHS as the grading system.

 

[BrocLuno]

I vote for Shannow

 

[fdcg27]

Originally Posted By: Shannow
If I had control, it would be XW-HTHS as the grading system.


Those are the lines along which I was thinking when I wrote the opening post.

 

[JHZR2]

40wt oils always did fine for my M42. I'd personally run a 5w-40 syn if it doesn't consume.

 

[SonofJoe]

A couple of points...

HTHS is a significantly more difficult and costly test to run than simple KV. At a rough guess, for any given oil development program, you might run two hundred KVs for every one HTHS you run. Most oils that you buy off the shelf (ie were made in a blend plant) won't have been tested for HTHS; only the master batch will have been tested to confirm it's ongrade.

Moving to xxW-HTHS denominated oils might be appropriate for thinner oils but not for heavier oils (15W40,:10W40, 15W50, 20W50) where HTHS is usually a slack variable.

The 3.5 min HTHS is a limit that grew out of some work by MB on bearings. The limit is to my knowledge at least 20 years old and is likely to be a decade older still. It dates from a time when all European oils were thick. Personally I don't get too fixated about the 3.5 number; it's an arbitrary limit. Is it any better than 3.4 say or 3.3? In the light of what's happened with 2.9 min oils in the US and other countries, my read of the situation is that 3.5 min, is, and always has been, too severe a limit.

Finally, it's worth saying that your driving style and where you live should inform your view as to whether you might need a 3.5 min HTHS oil. I doubt the oil in our little Suzuki ever approaches 150C (HTHS temp) because I drive like the Pope's mother and the UK climate in temperate (aka bloody miserable!). The 0W20 we have is fine.

 

[mjoekingz28]

Excuse any ignorance, but isnt HTHS basically the KV at 150 degrees Celcius?

 

[SonofJoe]

Originally Posted By: mjoekingz28
Excuse any ignorance, but isnt HTHS basically the KV at 150 degrees Celcius?


No. VII polymers in engine oil will shear when subjected to mechanical stress and lose part of their functionality. The level of shear in a standard Kinematic Viscosity 'tube drop' test is very low. The level of shear in the HTHS test is very high (the idea being that it mimics what happens in your big-end bearings). All things be being equal, and correcting for units, the HTHS will generally be lower than the KV150.

 

[FCD]

I think that on the labels of oil there should be the SAE Grade, and also the HTHS clearly on the label for example : SAE 10W-40- HTHS 3.5, SAE 20W-50- HTHS 5.0

 

[Shannow]

Originally Posted By: mjoekingz28
Excuse any ignorance, but isnt HTHS basically the KV at 150 degrees Celcius?


Particularly with the advent of the 10W40 grade, they found that the multigrades weren't protecting the same as their KVs would suggest, and they started investigating what happened, was that the oil under high shear conditions (like the bearings) thinned out due to the behaviour of the polymers...it behaved like a much lower viscosity oil.

Here's an excerpt from an early study showing that at certain RPM ranges (shear rate), the behaviour of the oil thinned somewhat markedly, 50s offering the protection of a 30.

So they introduced HTHS into the J300, and funnily enough, the HTHS minimum for a 0W, 5W, and 10W40 was exactly the same as the minimum for a 30...was corrected recently with technology improvements so that those grades now have to meet 3.5.

As to the KV150, here's a particular unicorn that wouldn't exist in a sensible world.

https://mobiloil.com/en/motor-oils/mobil-1/mobil-1-racing-oil

M1 Racing 0W50, is allegedly a 50 (it meets 50 KV100, and the HTHS minimums), but offers protection of a 0W/5W40 at high temperatures.

It's HTHS is 3.8 (note in Cp, which has to be converted to Cst)...making it 5.1Cst...it's KV150 should be 7.1, so it's 28% thinner than it should otherwise be.

 

[zeng]

Originally Posted By: SonofJoe
VII polymers in engine oil will shear when subjected to mechanical stress and lose part of their functionality.

Is there a likelihood in high shear areas like differential hypoid gears and cams/lifters or any other applications , VII completely lost its viscosity contribution temporarily ?
What about permanently lost its viscosity contribution.
Btw, can base oil operating at high temp and high shear, temporarily lost its viscosity?

 

[Garak]

Originally Posted By: SonofJoe
HTHS is a significantly more difficult and costly test to run than simple KV. At a rough guess, for any given oil development program, you might run two hundred KVs for every one HTHS you run. Most oils that you buy off the shelf (ie were made in a blend plant) won't have been tested for HTHS; only the master batch will have been tested to confirm it's ongrade.

It still wouldn't hurt to have them on the bottle or the data sheets as a matter of practice. Outside of BITOG members and the industry itself, almost no one would know the difference between an ILSAC 5w30 and an A3/B3 A3/B4 5w30 and an E6, E7, E9 5w30 when it comes to specifications, let alone viscosity nuances. The average person would consider them completely interchangeable.

 

[Shannow]

Originally Posted By: Garak
The average person would consider them completely interchangeable.


Which is what got the HTHS incorporated into J300 in the first place...they WERE considered interchangeable.

 

[mjoekingz28]

Leave it to Shannow to get all scientific.....with charts and graphs no less : )


Thank you for answering my next question and that was why they rate it on the mPa scale and not the KV......maybe the officials enjoy the complexity.



Thanks for the schooling sonofjoe and all!

 

[Solarent]

Originally Posted By: zeng
Originally Posted By: SonofJoe
VII polymers in engine oil will shear when subjected to mechanical stress and lose part of their functionality.

Is there a likelihood in high shear areas like differential hypoid gears and cams/lifters or any other applications , VII completely lost its viscosity contribution temporarily ?
What about permanently lost its viscosity contribution.
Btw, can base oil operating at high temp and high shear, temporarily lost its viscosity?


Anecdotally I would say that Viscosity Index Improvers (or viscosity modifiers) never completely loose their contribution to the HTHS, if anything after running through a high shear environment the worst that would happen would be some kind of permanent viscosity contribution loss (to the tune of 25-35% depending on the SSI of the polymer). Base oil alone does not exhibit the change in viscosity due to shearing in the same way that an oil with VII would. For extra information I suggest you read this: Rheology of Viscosity Modifiers and ULV Lubricants

 

[SonofJoe]

Originally Posted By: Shannow
Originally Posted By: mjoekingz28
Excuse any ignorance, but isnt HTHS basically the KV at 150 degrees Celcius?


Particularly with the advent of the 10W40 grade, they found that the multigrades weren't protecting the same as their KVs would suggest, and they started investigating what happened, was that the oil under high shear conditions (like the bearings) thinned out due to the behaviour of the polymers...it behaved like a much lower viscosity oil.

Here's an excerpt from an early study showing that at certain RPM ranges (shear rate), the behaviour of the oil thinned somewhat markedly, 50s offering the protection of a 30.

So they introduced HTHS into the J300, and funnily enough, the HTHS minimum for a 0W, 5W, and 10W40 was exactly the same as the minimum for a 30...was corrected recently with technology improvements so that those grades now have to meet 3.5.

As to the KV150, here's a particular unicorn that wouldn't exist in a sensible world.

https://mobiloil.com/en/motor-oils/mobil-1/mobil-1-racing-oil

M1 Racing 0W50, is allegedly a 50 (it meets 50 KV100, and the HTHS minimums), but offers protection of a 0W/5W40 at high temperatures.

It's HTHS is 3.8 (note in Cp, which has to be converted to Cst)...making it 5.1Cst...it's KV150 should be 7.1, so it's 28% thinner than it should otherwise be.



I don't know for sure but would guess that the 'problem' 10W40's you're talking about originated out of the US. This is what you get from trying to make an all Group I 10W40 with 50 SSI VII. God knows what the Noack of such an oil would be like but I'd guess at around 20%! In contrast, European 10W40's with a max Noack of 13% and made from 22 SSI VII would out of necessity, always be semi-synthetic and never shear to the extent you described.

The Mobil 0W-50 racing oil is a unicorn that should have been drowned at birth! What were they thinking??? Do people actually pay real money to buy this stuff?

 

[SonofJoe]

Originally Posted By: Garak
Originally Posted By: SonofJoe
HTHS is a significantly more difficult and costly test to run than simple KV. At a rough guess, for any given oil development program, you might run two hundred KVs for every one HTHS you run. Most oils that you buy off the shelf (ie were made in a blend plant) won't have been tested for HTHS; only the master batch will have been tested to confirm it's ongrade.

It still wouldn't hurt to have them on the bottle or the data sheets as a matter of practice. Outside of BITOG members and the industry itself, almost no one would know the difference between an ILSAC 5w30 and an A3/B3 A3/B4 5w30 and an E6, E7, E9 5w30 when it comes to specifications, let alone viscosity nuances. The average person would consider them completely interchangeable.


I fully agree with what you say but as per usual, this is always much more complicated than you might think.
I recall that a few years back, there was pressure to 'year reference' the ACEA specifications so that people might know whether they were getting say, ACEA A3/B3, as defined by the 1996 spec or A3/B3 2008 vintage; the latter being a completely different animal. I believe this was vetoed on some spurious basis with one oil company claiming that year referencing the spec was a restraint on free trade!
It's a bit of a cynical view but I think it's fairly obvious that it suits the industry just fine to restrict the amount and quality of information they provide to the general public. That way we can't compare things, can't ask awkward questions and are more easily led down the path they want to go down.

 

[Solarent]

Isn't the ACEA specification supposed to be evergreen? IE if you are claiming it you have to conform to the current version of the spec and if you don't then you fall afoul of advertising laws?

This is true with the API starburst and the Dexos1/Dexos2 labels.

 

[bulwnkl]

Yep. That same marketing (to those who are just certain they need a 50-grade oil) is why the Mobil 0w50 racing oil exists.

 

[bulwnkl]

Originally Posted By: Solarent
Isn't the ACEA specification supposed to be evergreen? IE if you are claiming it you have to conform to the current version of the spec and if you don't then you fall afoul of advertising laws?


Not outside of Europe. And I seriously doubt it's afoul of advertising 'laws' to do so with dexos, either, though I expect it's a violation of the terms of the dexos license to do so.