Rethink and understand SAE viscosity: a 0W-20 can be thicker than a 0W-40 or 5W-40

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This is my conclusion about the SAE J300 viscosity specification: It is obsolete and does not give the full picture.

SAE J300 was updated in the mid-1990s to correct inherent problems associated with it by introducing the HTHS viscosity, which is measure at 150 ℃ and a shear rate of 10⁶ s⁻¹. At that time, viscosity meters were limited to a shear rate of 10⁶ s⁻¹. However, the HTHS viscosity does not directly relate to engine wear.

Recently viscometers capable of measuring at shear rates of 10⁷ s⁻¹ have become possible. I introduced the HTFS viscosity, which is measured at a shear rate of 10⁷ s⁻¹ or higher (as shear rate → ∞).

The HTFS viscosity will determine the wear protection of an oil—higher HTFS for more wear protection. HTFS and viscosity index (VI) will determine the fuel economy—lower HTFS and higher VI for better fuel economy.

If my table is sorted by HTFS, you will see that some 0W-20 oils are thicker than some 0W-40 oils. For example, Ravenol ECS 0W-20 is thicker than M1 FS 0W-40. Therefore, before you get into any "thick vs. thin" debate, understand that the SAE viscosity grade does not paint the whole picture and a 0W-20 can actually be very thick.

HTFS and VII-content table sorted in decreasing HTFS

 

ZeeOSix

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However, the HTHS viscosity does not directly relate to engine wear.
Are there any controlled tests that prove how far off the HTHS vs wear rate correlation is? Or is this all just theory without verification?

In order to get some non-correlation, engines would have to be ran at pretty high RPM to get the oil to shear near maximum values.

Why don't motorcycles that rev to 10,000 to 15,000 RPM (and obviously put oil into some crazy shear rates) use xW-20 or thinner oils if viscosity and HTHS doesn't have a bearing on engine wear? Or why don't high performance cars like Mustangs, Corvettes, etc say it's OK to use xW-20 or thinner oils for track use where the engine is near redline for most of the time? If it protected just as good or better you'd think they would be specifying thin oils for track use to get more HP out of the engine for the "win". Or cars like the Mustang GT500 and the Corvette coming with 5W-50 and 0W-40 from the factory in the sump? If thinner oil was just as good or better for engine protection due to the HTHS (or HTFS), those cars would come from the factory with thinner oil to reap the benefits of better fuel mileage (and CAFE) and more HP.
 
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Aaaaaaaandddd...
Here we go.

Nothing to add at this time except that a shear-stable thick 20 at 2.9 is technically the thinnest 30 grade. Redline 0W-20 has this HTHS and is labeled a 0W-20. As far as I know, it does not shear. Group V.

Now let's see where the topic goes.

02_Viscosity-Image3_500w.jpg
 

ZeeOSix

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Redline 0W-20 has this HTHS and is labeled a 0W-20. As far as I know, it does not shear. Group V.
If its KV100 was between 9.3 cSt and less than 12.5 cSt, then it should have been labeled as a 30 grade. Did it not meet the KV100 spec for 30 grade? Got a link to the specs?
 
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Aaaaaaaandddd...
Here we go.

Nothing to add at this time except that a shear-stable thick 20 at 2.9 is technically the thinnest 30 grade. Redline 0W-20 has this HTHS and is labeled a 0W-20. As far as I know, it does not shear. Group V.

Now let's see where the topic goes.

View attachment 123296
Good info. Being a pedestrian, I haven't seen that table before. Thank you for that.
 

Gokhan

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Are there any controlled tests that prove how far off the HTHS vs wear rate correlation is? Or is this all just theory without verification?

In order to get some non-correlation, engines would have to be ran at pretty high RPM to get the oil to shear near maximum values.

Why don't motorcycles that rev to 10,000 to 15,000 RPM (and obviously put oil into some crazy shear rates) use xW-20 or thinner oils if viscosity and HTHS doesn't have a bearing on engine wear? Or why don't high performance cars like Mustangs, Corvettes, etc say it's OK to use xW-20 or thinner oils for track use where the engine is near redline for most of the time? If it protected just as good or better you'd think they would be specifying thin oils for track use to get more HP out of the engine for the "win". Or cars like the Mustang GT500 and the Corvette coming with 5W-50 and 0W-40 from the factory in the sump? If thinner oil was just as good or better for engine protection due to the HTHS (or HTFS), those cars would come from the factory with thinner oil to reap the benefits of better fuel mileage (and CAFE) and more HP.
Chevron, Nissan, and others studied it.


 
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OVERKILL

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Aaaaaaaandddd...
Here we go.

Nothing to add at this time except that a shear-stable thick 20 at 2.9 is technically the thinnest 30 grade. Redline 0W-20 has this HTHS and is labeled a 0W-20. As far as I know, it does not shear. Group V.

Now let's see where the topic goes.

View attachment 123296
It's mostly PAO, got any other spurious posits you'd like to make?
 
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Same here. They still advertise "Ester based oil" on their website. No mention of PAO base. Copy and paste from their 20W-50:

  • Full-synthetic ester formula for passenger cars, light trucks, performance vehicles and marine applications
Despite the obvious chemical diff, thot Grp IV and V's were similar in terms of performance. I wonder what the key differences are. It appears PAO's are less expensive for the blender? Hmm...
 
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Despite the obvious chemical diff, thot Grp IV and V's were similar in terms of performance. I wonder what the key differences are. It appears PAO's are less expensive for the blender? Hmm...
Yep, and if my memory serves me correctly, didn't the pao thing begin when P66 bought out Redline?
 
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At my age, I’ve had all the “reimagining” that I can take 😂
I suppose maximizing profits remains the "name of the game" for most, if not all, of the mfgrs and blenders. And or how much they can get away with... :cool:

I suppose that's why we crazies here are so bloody mindful? :)

HPL appears to do its best to produce a top-notch product regardless. They do charge for that premium product though ... as they should. :)
 
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Same here. They still advertise "Ester based oil" on their website. No mention of PAO base. Copy and paste from their 20W-50:

  • Full-synthetic ester formula for passenger cars, light trucks, performance vehicles and marine applications
Thank you... ", got any other spurious posits you'd like to make?"

lol.

They also go on to say this:
  • Blended with polyol ester base stocks that feature natural multi-grade properties, avoiding unnecessary additives that hinder lubricity

Hey.

I appreciate knowing I wasnt coming out of nowhere. Thank you @aquariuscsm
 
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