HTHSv and xw30 vs xw40 choice

[A_Harman]

Originally Posted By: Joe90_guy
Typically a European 5W30 is limited by 3.5 min HTHS. A lot of these oils are formulated with Shellvis VIs which have good polymeric efficiency but relatively poor HTHS performance. Typically a 5W30 will have a high KV100 to make the 3.5 min HTHS (12.0 cst isn't uncommon). These oils aren't limited by KO30 shear.
The corresponding 5W40 will almost certainly be limited by KO30 shear before it's limited by HTHS (3.7 min if API specs are part of the spec claim). Even with Shellvis, you're probably talking about an actual 3.9 HTHS if the oil is going to meet 12.5 min after KO30.
Hope this helps...


There's some new terminology for me.
KO30 = Kurt Orbahn test, 30 passes?
Isn't the standard KO test 90 passes?

 

[Joe90_guy]

On ACEA A3/B3/B4 it's still 30 cycle. Think they're using 90 cycle for some HDDO these days. If they used 90 cycle on PCMO they it's bye bye Shellvis and bye bye top tier Euro gunk.

 

[alcyon]

Originally Posted By: Joe90_guy
On ACEA A3/B3/B4 it's still 30 cycle. Think they're using 90 cycle for some HDDO these days. If they used 90 cycle on PCMO they it's bye bye Shellvis and bye bye top tier Euro gunk.

interesting..when you say bye bye euro gunk..do you mean that the hths drops in the 90 cycles test ?
also..which grade can meet the 90 cycles test ?

 

[Joe90_guy]

The HTHS test and the Kurt Oban shear test are two distinct tests.
The KO test pushes oil through a fuel injector to induce permanent shearing of the oil. Once the test is complete, you simply measure the standard kinematic viscosity of the oil at 100C. The result is then compared to the lower KV100 limit of your vis grade (12.5 min for an 5W40 or 9.3 min for a 5W30. I suspect if you took the sheared oil from KO and put it through HTHS it might be lower than normal but I've never run that test.
As you might expect, running a 90 cycle KO is more extreme than a 30 cycle test. It's not, as you might expect, three times more extreme as there's a limit to how much you can chew up VI molecules.
Shellvis VI is 'clever' in that it's pretty good on KO30 even though it's relatively poor on HTHS. However if you extend KO out to 90 cycles, its inherent fragility becomes more apparent. Thinking about this, this wouldn't affect 5W30 Euro top tier but 5W40 & 0W40 would be impacted.
Euro OCP VIs tend to be far more robust so wouldn't be greatly affected by a switch from 30 to 90 cycles. However, doing top tier with OCP is far from easy as you are dealing with so much more rubber in the oil.
Hope this helps...

 

[Benito]

Joe90_guy, are you saying that the reason why "Euro" xw40 have a higher HTHS is so they can meet the KO shear test (which is different for xw40 than for xw30 from a results perspective because it is based on KV100 staying in grade)?

 

[alcyon]

Originally Posted By: Joe90_guy
The HTHS test and the Kurt Oban shear test are two distinct tests. However if you extend KO out to 90 cycles, its inherent fragility becomes more apparent. Thinking about this, this wouldn't affect 5W30 Euro top tier but 5W40 & 0W40 would be impacted..

is this attributed to the higher VI added. Sorry..i am pretty new to this..do you mean a 5w40 and 0w40 will drop from 40grade cst to lower than 30grade min cst when permenantly sheared. And a 30 grade acea a3/b4 will perhaps drop just a little..

 

[Benito]

I think he's saying that an xw40 will experience a greater shear in KV than a xw30 and that shear will take the xw40 out of grade. Thus the xw40 has to have a higher HTHSv.

I think I've finally had my original question answered!

 

[Joe90_guy]

Yes. That's exactly it...

 

[Joe90_guy]

It might be worth saying that the KO30 shear test isn't used on US PCMOs for the simple reason that the great majority of US oils would fail the test! The US differs greatly from Europe in that you use highly shearable 50 SSI VIs. These are very cheap and great for passing fuel economy tests but otherwise they are pretty useless. I'm sure this situation only endures in the US because you change your oil so frequently.

 

[Joe90_guy]

If you look in the VOA section, some kind soul has just posted up an analysis of Walmart Supertech Synthetic 5W30.
I'm not sure why but the analysis includes a KO30 shear result. It shows the KV100 of the oil shearing down from 11.02 cst to 8.85 cst. Under ACEA rules, this would be classed as shearing out of grade and not allowed. It's pretty clear that this is a consequence of the oil being formulated with highly shearable 50 SSI VII. You could probably get the oil to stay-in-grade by pushing the KV100 of the oil to about 11.6 ish but then you might find yourself struggling to pass your fuel economy test.
I'm only flagging this up as it illustrates how KO30 shear and HTHS are different tests measuring different things and you have to check one is the limiting factor in a given blend.

 

[chrisri]

But a member here answered my question about relation between kinematic and dynamic viscosity polymers, and if I recall correctly they are not directly connected. Different types of polymers are used to boost up HTHS.

 

[Joe90_guy]

I think you've been mislead a little. There's only one class of polymers that go into modern oils and that's VII. Most are Olefin Co-Polymers (OCPs). There are some Isoprene-Styrene VIIs which are more efficient but perform the same basic functions. Any VIIs will boost both Kinematic Viscosity and Dynamic Viscosity over a wide range of temperatures. They all boost HTHS and KV100 after shear to greater or lesser degrees. You friend might by thinking of Pour Point Depressants which are also polymers (usually polymethacrylates) but these are added to oils at such low dosages they have no material effect on the oil's viscometric.

 

[chrisri]

OK, so what is the difference between ILSAC /API 5w30 and a Euro 5w30 if both have similar kinematic viscosity, yet they differ in dynamic viscosity severely?
As you've mentioned earlier American oils use different polymers to achieve desired KV spec, and are share prone. Is difference only in polymers or is there something else?

Thanks!

 

[Joe90_guy]

I guess it depends if you see 50 SSI VII and 22 SSI VII as 'different' polymers. I tend to think of them as different variants of the same thing. You can make a 22 SSI OCP simply by shearing down 50 SSI rubber to make the polymer chains a bit shorter. Low SSI is used in Europe because OEMs and ACEA adopted KO30 shear and weren't quite so neurotic about fuel economy as the Americans. The Americans probably thought the Europeans were being overly restricted and stuck with high SSI which works out the cheaper option. Both positions are understandable. But it's not like one VII targets Kinematic while the other targets Dynamic. Trust me, it just doesn't work that way...

 

[OVERKILL]

Originally Posted By: Joe90_guy
The HTHS test and the Kurt Oban shear test are two distinct tests.
The KO test pushes oil through a fuel injector to induce permanent shearing of the oil. Once the test is complete, you simply measure the standard kinematic viscosity of the oil at 100C. The result is then compared to the lower KV100 limit of your vis grade (12.5 min for an 5W40 or 9.3 min for a 5W30. I suspect if you took the sheared oil from KO and put it through HTHS it might be lower than normal but I've never run that test.
As you might expect, running a 90 cycle KO is more extreme than a 30 cycle test. It's not, as you might expect, three times more extreme as there's a limit to how much you can chew up VI molecules.
Shellvis VI is 'clever' in that it's pretty good on KO30 even though it's relatively poor on HTHS. However if you extend KO out to 90 cycles, its inherent fragility becomes more apparent. Thinking about this, this wouldn't affect 5W30 Euro top tier but 5W40 & 0W40 would be impacted.
Euro OCP VIs tend to be far more robust so wouldn't be greatly affected by a switch from 30 to 90 cycles. However, doing top tier with OCP is far from easy as you are dealing with so much more rubber in the oil.
Hope this helps...


Great posts in this thread!

I'm guessing you work in the industry by the detail provided?

 

[Benito]

^ he's a retired oil formulator. I'm going to guess for Shell.

And I agree it's great info. And he's making it really easy to understand.

 

[alcyon]

There seems to be a correlation between kv100 cst and hths. I notice all the acea a3/b4 30wts seem to have a higher cst at 100c. For instance shell helix ultra 5w30 is 12.2 and helix hx7 5w30 is 11.9. Both have min hths of 3.5.
and the ilsac gf5 oils like eneos sustina and PU 5w30 kv100 at 10.3. Hths 2.9.
the helix ultra 40wts kv100 is 13.1. Not much higher than the 30wts.

 

[Garak]

There should be some sort of correlation. After all, SAE grades are delineated by KV100. Higher SAE grades tend to also have higher HTHS.

 

[Joe90_guy]

For most of what goes into oil, the correlation between KV100 and HTHS is almost 1-to-1. I say almost because KV100 is measured in centistokes whereas HTHS is measured in centipoise and you would need to correct for density to get a better correlation. The reason for this correlation is that most of what goes into oil, stuff like base oils and common DI components, does not shear.
The big exception to the rule is VII. VII molecules are very long and can shear especially under the influence of high temperature and mechanical force. Shear a VII molecule and its ability to boost viscosity at high temperatures drops. Let me be clear. VIIs on the whole are pretty robust in real life. Even under the extreme conditions of the HTHS and KO30 tests, you typically only see a lowish level of shear but in the game that is oil formulation, you have to take all of this stuff into account. As I have said before, shear afflicts US oils much more than just about any other part of the world because only the US still uses high SSI VII. However the US specs accommodate this fact and probably always will.

PS - to the person that asked, yes I am ex-industry but no it wasn't Shell (thank God!)

 

[Garak]

I think North America (and Japan to some extent) has used short OCIs as a crutch for various things for a lot of years. So, it sounds like you're happy you weren't working for Shell? I suppose all the companies have their little quirks that can drive employees off the deep end.