HTHSv and xw30 vs xw40 choice

[Benito]

HTHS viscosity is more important than grade.

The Euro oils must all have a minimum HTHSv of 3.5 regardless of if they are xw30 or xw40.

However, Porsche and AMG require oils that are xw40 and not xw30.

So if HTHSv is the most important thing, any idea on their reasoning to specify this by grade instead of HTHSv? Or does the Porsche spec require a higher HTHSv? (MB 229.5 doesn't as far as I know though)

Would a xw40 with an HTHSv of 3.5 be more suitable than a xw30 with an HTHSv of 3.6 for example?

 

[userfriendly]

Add 15W30 with HTHS of 3.7 and SAE 30 with 3.8

 

[901Memphis]

Probably because your average consumer doesn't want to learn the differences between kinematic viscosity and dynamic viscosity

 

[Peter_M]

Originally Posted By: Benito
HTHS viscosity is more important than grade.

The Euro oils must all have a minimum HTHSv of 3.5 regardless of if they are xw30 or xw40.

However, Porsche and AMG require oils that are xw40 and not xw30.

So if HTHSv is the most important thing, any idea on their reasoning to specify this by grade instead of HTHSv? Or does the Porsche spec require a higher HTHSv? (MB 229.5 doesn't as far as I know though)

Would a xw40 with an HTHSv of 3.5 be more suitable than a xw30 with an HTHSv of 3.6 for example?


MB 229.5 specifies a HTHS of greater than 3.5 and doesn't preclude xW-30 grades on the spec table I have.

I understand Porsche specifies a HTHS greater than 3.5 as well but I'm not sure whether that's just a result of the A40 oils meeting the ACEA A3/B3/B4 spec as well.

The fact that all the A40 certified oils are Xw-40 and Xw-50 I think just indicates we are creatures of habit and the market expects to see these grades. Maybe it's as simple as none of the oil manufacturers have paid Porsche to have one of their xw-30 oils certified!

I say we are creatures of habit as Porsche Classic - their parts arm for older cars - introduced their own 20w-50 and 10w-60 range about two years ago that has absolutely no API or ACEA classification and not even their own A40 certification. They say they selected the SAE grades because the "market" they were selling to indicated they were the grades they expected to see!

I think a lot of what we have is the result of historic circumstances and if we started from scratch today the whole classification system would be much simplier.

Regards

 

[Benito]

Thanks Peter.

You can see the xw40 requirement for AMG engines here:

https://bevo.mercedes-benz.com/d/d/en/Spec_223_2.pdf

 

[chrisri]

Dynamic viscosity minimum limit was introduced to protect engine bottom end. Kinematic viscosity is still important either for protection or for proper function of some parts of the engine. Hydraulic valve adjusters, tensioners, VVT all depend on KV100 viscosity.

 

[Benito]

Thanks chrisri.

Does anyone else have thoughts on this topic?

 

[edyvw]

Originally Posted By: Benito
Thanks chrisri.

Does anyone else have thoughts on this topic?

I think there are several variables here.
A40 requirement for 40 weight (although first versions of GC 0W30 met A40), is due to ignorance of a lot of drivers, and mechanics. Why explaining HTHS when you could just mandate W40 ACEA A3/B3 that would meet required HTHS. I bet a lot of W30 Euro oils would be fine in Porsche, but then you are opening Pandora box. A lot of drivers would think any 5W30 oils would be fine. It is the case with other Euro cars where people put anything in the engine as long as it is same grade, not thinking about HTHS, NOACK etc.

 

[userfriendly]

None of all this was a concern before the light weight
engine oil craze hit.
Soon anything thicker than 0W16 will be politically incorrect.

Who can be the most organic challenge, as one member put it....
holding hands and singing Kumbayah.

I'll take an engine oil that is thicker than necessary than
one that is too thin.

 

[edyvw]

Originally Posted By: used_0il
None of all this was a concern before the light weight
engine oil craze hit.
Soon anything thicker than 0W16 will be politically incorrect.

Who can be the most organic challenge, as one member put it....
holding hands and singing Kumbayah.

I'll take an engine oil that is thicker than necessary than
one that is too thin.

On that note: how they come up with 0W16 not 0W15?

 

[userfriendly]

Because the Germans couldn't pronounce 5W/15W

 

[edyvw]

Originally Posted By: used_0il
Because the Germans couldn't pronounce 5W/15W

lol

 

[Benito]

Originally Posted By: edyvw
Originally Posted By: Benito
Thanks chrisri.

Does anyone else have thoughts on this topic?

I think there are several variables here.
A40 requirement for 40 weight (although first versions of GC 0W30 met A40), is due to ignorance of a lot of drivers, and mechanics. Why explaining HTHS when you could just mandate W40 ACEA A3/B3 that would meet required HTHS. I bet a lot of W30 Euro oils would be fine in Porsche, but then you are opening Pandora box. A lot of drivers would think any 5W30 oils would be fine. It is the case with other Euro cars where people put anything in the engine as long as it is same grade, not thinking about HTHS, NOACK etc.


That may answer the Porsche question but not the AMG question.

 

[edyvw]

Originally Posted By: Benito
Originally Posted By: edyvw
Originally Posted By: Benito
Thanks chrisri.

Does anyone else have thoughts on this topic?

I think there are several variables here.
A40 requirement for 40 weight (although first versions of GC 0W30 met A40), is due to ignorance of a lot of drivers, and mechanics. Why explaining HTHS when you could just mandate W40 ACEA A3/B3 that would meet required HTHS. I bet a lot of W30 Euro oils would be fine in Porsche, but then you are opening Pandora box. A lot of drivers would think any 5W30 oils would be fine. It is the case with other Euro cars where people put anything in the engine as long as it is same grade, not thinking about HTHS, NOACK etc.


That may answer the Porsche question but not the AMG question.

I would say it is a same thing. AMG engines are under more stress, so why not go with W40 weight and with that avoid confusion.

 

[Benito]

But you've seemed to miss the details in my opening question.

A xw30 can have a higher HTHSv than a xw40. And we've been told that HTHSv is more important than grade.

So in what way is the xw40 guaranteed to be tougher than the xw30? chrisri touched upon a possible reason. What do you think of that?

 

[Shannow]

Benito,
I would posit that a 3.5HTHS 5W30 is superior to the same HTHS in a 5W40.

The 5W30 will have heavier basestocks (better volatility), less VII (temporary and permanent shear and sludge/varnish), and less (tiny really) wasted energy in the places that the KV is dominant.

Provided it's got non ILSAC/SM/SN additive levels.

 

[Benito]

Thanks Shannow.

So the implication is that AMG, and maybe also Porsche, specify xw40 for the benefit of protection for other parts of the engine.

This is what chrisri also said, but it's good to get more confirmation.

 

[userfriendly]

The 5W40 I use has a HTHS of 4.3-4.4 and the 0W40 4.1
If I want 3.6; 5w30, 10W30 or SAE 30 will do for half the price.
The 10W40 syn and 15W40 blends both are 4.5< HTHS.

 

[Shannow]

Originally Posted By: Benito
Thanks Shannow.

So the implication is that AMG, and maybe also Porsche, specify xw40 for the benefit of protection for other parts of the engine.

This is what chrisri also said, but it's good to get more confirmation.


Honestly, I'm struggling to think of any region that would require a greater KV, particularly in the 30/40 grade.

The high shear areas will be protected by HTHS, and the low shear rate areas become high shear rate as the oil film thickness reduces.

Hydraulics would be working on KV, and their leakage rates are too. Honda mention problems on ultra low viscosity with phasers and the like, with the leakage and oil pressure that comes with ultra low viscosity oils.

But like I said, I can't see that as being a reason to pick more VII, more volatility between the 30s and 40s.

 

[Quattro Pete]

Originally Posted By: Benito
A xw30 can have a higher HTHSv than a xw40.

Theoretically, sure. Can you list some real life examples though, from the ones that officially meet mfg approvals?