HTHS vis spec trumps the Kinematic 100C vis spec'

[rrrrrroger]

I read this.
I am confused.
I see now why EV drivers say their cars are so, so much simpler to understand and maintain. (Well except for the battery which has a chemistry as complicated as oil chemistry.)

 

[Shannow]

Originally Posted By: Vincenzo_f
Supposing we have two oils, with the same value and the same HTHS value and same VI, but with different grade, example:
5w30 with VI 170 and HTHS 3.6
5w40 with VI 170 and HTHS 3.6

Ambient temperature is the same (68°F).
The action of the two oils will be the same?
What changes is the flow of the pressure?


http://www.pecj.or.jp/japanese/report/e-report/01M445e.pdf

Quote:
(1) By lowering HTHS viscosity in increments of 0.5 mPa·s, a low friction effect of about 3% was measured. The relationship between HTHS viscosity and fuel economy is well-known, but in the present research, it was clarified that fuel economy is high even when the HTHS viscosity is in the ultra-low region of 2.1 mPa·s.

(2) It was discovered that a lower friction effect of about 3% can be gained by lowering the CCS viscosity.

(3) Even at the same HTHS viscosity, fuel economy was found to be high when the CCS viscosity is low. This suggests that on the lubricated surfaces inside a practical engine, the shear conditions are more severe than in a HTHS viscosity measurement and that an even higher fuel economy could be gained with alternative formulation technology for base oil or viscosity index improver.

 

[rrrrrroger]

" it was clarified that fuel economy is high even when the HTHS viscosity is in the ultra-low region of 2.1 mPa·s."

It sounds like if you go too low with HTHS, metal on metal contact will decrease fuel economy. And that CCS viscosity matters more.

 

[tudorart]

'Even at the same HTHS viscosity, fuel economy was found to be high when the CCS viscosity is low. This suggests that on the lubricated surfaces inside a practical engine, the shear conditions are more severe than in a HTHS viscosity measurement and that an even higher fuel economy could be gained with alternative formulation technology for base oil or viscosity index improver.'

I'm still reading on it but I wonder if that's from more polymers that sheared permanently and hence gave consequently lower/aged HTHS figures and better fuel economy. I tried to find whether or not this was done on fresh juice or it's been worked up quite a bit before the results...very good read so far, Thanks

Also same HTHS but different VI will give you lower HTHS viscosity on the whole HTHS spectrum up to 150C (where they meet) for the highest VI fluid. So unless you're right at 150C two fluids with different VI's shouldn't be able to have the same HTHS viscosity and consequently fuel economy.

Am I seeing this right?

 

[rrrrrroger]

I just figured the viscosity of the oil is a bigger factor in Fuel economy than the oil shear between two metal surfaces.

If I were picking an "ideal" oil I would want the thinnest 100C viscosity possible, but with high HTHS values to prevent wear.

 

[CATERHAM]

Originally Posted By: tudorart

Also same HTHS but different VI will give you lower HTHS viscosity on the whole HTHS spectrum up to 150C (where they meet) for the highest VI fluid. So unless you're right at 150C two fluids with different VI's shouldn't be able to have the same HTHS viscosity and consequently fuel economy.

Am I seeing this right?

That's exactly right and is the main reason the OEM 0W-20s have very high VIs. There is a very large difference in operational viscosity between a 150 VI 5W-20 and a 200+ VI 0W-20. It's quite dramatic on cold start-ups but is also is also quite significant at normal operating temp's, the 0W-20's still being lighter. That's because, as you pointed out, they all have the same nominal HTHSV @150C of 2.6cP.

 

[CATERHAM]

Originally Posted By: rrrrrroger

If I were picking an "ideal" oil I would want the thinnest 100C viscosity possible, but with high HTHS values to prevent wear.

That's not going to help you much.
The point of this thread is that if know the HTHSV you can ignore the KV100 spec' but not the oils VI particularly with light 20wt oils. The following thread (courtesy asharris7) explains why you can't "Ignore Viscosity Index":

http://www.machinerylubrication.com/Read/28956/lubricant-viscosity-index

To pick the ideal oil in terms of viscosity you want an oil with both the highest HTHSV and VI rating that still provides the minimum optimum operational viscosity when the oil is fully hot.

 

[RamFan]

Originally Posted By: CATERHAM
Originally Posted By: rrrrrroger

If I were picking an "ideal" oil I would want the thinnest 100C viscosity possible, but with high HTHS values to prevent wear.

That's not going to help you much.
The point of this thread is that if know the HTHSV you can ignore the KV100 spec' but not the oils VI particularly with light 20wt oils. The following thread (courtesy asharris7) explains why you can't "Ignore Viscosity Index":

http://www.machinerylubrication.com/Read/28956/lubricant-viscosity-index

To pick the ideal oil in terms of viscosity you want an oil with both the highest HTHSV and VI rating that still provides the minimum optimum operational viscosity when the oil is fully hot.


How is that different than merely picking the highest HTHSV? Something you often argue against.

 

[Garak]

Originally Posted By: RamFan
How is that different than merely picking the highest HTHSV?


CATERHAM used a qualifier: "...the highest HTHSV and VI rating that still provides the minimum optimum operational viscosity when the oil is fully hot." That doesn't mean 5w-50.

 

[CATERHAM]

Because you can't ignore the VI.
If you just choose a higher HTHSV oil you'll just get a heavier oil at all oil temp's. Choosing an oil with a higher VI allows you to run a higher HTHSV oil without necessarily increasing the actual operational viscosity of oil at temp's below 150C.

I'll give an example.
The Idemitsu SM 0W-20 has a 200 VI, the Nippon Oil made Toyota 0W-20 a 214 VI and Sustina 0W-20 a 229 VI. All three oils have the same 2.6cP HTHSV @150C but the Toyota oil is lighter at normal operating temp's than the lower VI Idemitsu oil and the very high VI Sustina is lighter than the Toyota oil.
I'm running the Sustina oil but I want to maintain the same hot operational viscosity as the Idemitsu oil. To do so I've had to increase the HTHSV to approximately 2.75cP (by adding just over 10% of Sustina 0W-50). The end result is that I have an oil that is still lighter on start-up to the other two oils although I'm running a higher HTHSV rated oil; the best of both worlds.

 

[RamFan]

Originally Posted By: Garak
Originally Posted By: RamFan
How is that different than merely picking the highest HTHSV?


CATERHAM used a qualifier: "...the highest HTHSV and VI rating that still provides the minimum optimum operational viscosity when the oil is fully hot." That doesn't mean 5w-50.


I understand that. But, GC provides the minimum operational viscosity for my Charger which specifies 5/10w30. However GC is much thicker than most other w30 oils. Since GC has the highest HTHSV, why is it "ideal"?

 

[Garak]

It's not ideal. The highest HTHSV and VI rating that still provides.... would be a 5w-30 with a high VI and higher than the minimum HTHSV would be something like PP 5w-30.

You don't want the highest HTHS - that's not what he meant. You can't look at the HTHS without paying attention to VI for one. If you were looking simply for the highest HTHS you could find, you'd use a straight 50 in all applications. If you're looking for the highest VI and the highest HTHS possible, you'd be looking at a 0w-50 or something similar in all applications. That's clearly not what he meant.

 

[RamFan]

Originally Posted By: CATERHAM
Because you can't ignore the VI.
If you just choose a higher HTHSV oil you'll just get a heavier oil at all oil temp's. Choosing an oil with a higher VI allows you to run a higher HTHSV oil without necessarily increasing the actual operational viscosity of oil at temp's below 150C.

I'll give an example.
The Idemitsu SM 0W-20 has a 200 VI, the Nippon Oil made Toyota 0W-20 a 214 VI and Sustina 0W-20 a 229 VI. All three oils have the same 2.6cP HTHSV @150C but the Toyota oil is lighter at normal operating temp's than the lower VI Idemitsu oil and the very high VI Sustina is lighter than the Toyota oil.
I'm running the Sustina oil but I want to maintain the same hot operational viscosity as the Idemitsu oil. To do so I've had to increase the HTHSV to approximately 2.75cP (by adding just over 10% of Sustina 0W-50). The end result is that I have an oil that is still lighter on start-up to the other two oils although I'm running a higher HTHSV rated oil; the best of both worlds.

And you're certain you're only increasing the OT viscosity and not also start up viscosity because of your oil pressure gauge? No other indicator in the oil specs that I'm missing?

As an add on. When you've got two oils of the same grade, one with an HTHSV of 2.6 and a VI of 175, the other an HTHSV of 2.75 but a VI of 190 how can you tell on paper which is lightest at start up? Oil b has a higher viscosity but also has a higher VI but a is lower viscosity oil.

 

[kr_bitog]

Originally Posted By: CATERHAM

To pick the ideal oil in terms of viscosity you want an oil with both the highest HTHSV and VI rating that still provides the minimum optimum operational viscosity when the oil is fully hot.

isn't that typically refer to kv100 ?

 

[Shannow]

Nope, in reality the KV and the HTHS are tests that attempt to be representative of the things that happen inside an engine.

HTHS proves that KV100 isn't what's happening in the high shear areas, and there is evidence that HTHS isn't that good in areas like cams etc....but it's a far better measure.

Not to put words into CATERHAM's mouth, the operational viscosity is that which exists and is required in a location, and his method is to find the HTHS value that provides the minimum operational (required in that location) viscosity, then back it with the highest VI, which means that it's the thinnest that it can be when cold.

 

[CATERHAM]

Originally Posted By: RamFan
Originally Posted By: CATERHAM
Because you can't ignore the VI.
If you just choose a higher HTHSV oil you'll just get a heavier oil at all oil temp's. Choosing an oil with a higher VI allows you to run a higher HTHSV oil without necessarily increasing the actual operational viscosity of oil at temp's below 150C.

I'll give an example.
The Idemitsu SM 0W-20 has a 200 VI, the Nippon Oil made Toyota 0W-20 a 214 VI and Sustina 0W-20 a 229 VI. All three oils have the same 2.6cP HTHSV @150C but the Toyota oil is lighter at normal operating temp's than the lower VI Idemitsu oil and the very high VI Sustina is lighter than the Toyota oil.
I'm running the Sustina oil but I want to maintain the same hot operational viscosity as the Idemitsu oil. To do so I've had to increase the HTHSV to approximately 2.75cP (by adding just over 10% of Sustina 0W-50). The end result is that I have an oil that is still lighter on start-up to the other two oils although I'm running a higher HTHSV rated oil; the best of both worlds.

And you're certain you're only increasing the OT viscosity and not also start up viscosity because of your oil pressure gauge? No other indicator in the oil specs that I'm missing?

As an add on. When you've got two oils of the same grade, one with an HTHSV of 2.6 and a VI of 175, the other an HTHSV of 2.75 but a VI of 190 how can you tell on paper which is lightest at start up? Oil b has a higher viscosity but also has a higher VI but a is lower viscosity oil.

Yes I am increasing the cold start-up viscosity but not significantly and hardly noticeably in terms of cold start-up oil pressure. The lowered VI of the thickened up Sustina 0W-20 is about 223.

As to your second question, unfortunately we don't have enough typical PDS viscosity spec's to predict precisely which will be lighter. If we had a second HTHSV measure at say 100C then we could but it's rarely provided. What we do have available are the KV40 spec's, and while it is a kinematic measure with all it's limitations, if the oils being compared have similiar chemistries it will at least give you an idea.
Using the above example, the Sustina 0W-20 has a KV40 of 32.69cSt and the 0W-50 a KV40 of 95.43cSt. The blend I'm using increased the calculated KV40 to 36.66cSt which is significantly lower than the KV40 spec' of 39.94cSt for the Idemistsu oil and the 39.3cSt for the Toyota oil. It is still lower than the 37.4cSt for the latest Mobil made Toyota SN 0W-20 but not the new Idemitsu made Mazda SN 0W-20 at 35.?cSt and it's 221 VI.
Again, these are kinematic measures which should be taken as loose approximations of what one might expect in comparing how light these oils will be on start-up particularly at non extreme temp's at room temp's and above.

 

[kr_bitog]

Just a question on this:
PU 5w-30 vis@40 57.5 vis@100 10.3 HTHS 3.1 VI 169
M1EP 5w-30 vis@40 59.8 vis@100 10.6 HTHS 3.0 VI 169
M1 0w-30 vis@40 62.9 vis@100 10.9 HTHS 3.0 VI 166

So how do we interpret which should be thicker/better based on this thread topic ?

 

[A_Harman]

Those two oils are so close in their viscosity characteristics, you would be hard-pressed to see any difference in performance between them.

 

[kr_bitog]

Originally Posted By: A_Harman
Those two oils are so close in their viscosity characteristics, you would be hard-pressed to see any difference in performance between them.

yeah i think so, but just wonder what i should expect on the city driving scenario, which will give higher oil pressure during startup and normal operating temperature ?

 

[CATERHAM]

I agree those viscosity spec's are very close indeed, so much so that very little OP difference will be noticed on start-up or at normal operating temp's.
Although if you included PP 5W-30 (VI 177, HTHSV 3.0cP) which is lighter, it should be reflected in slightly lower OP most noticeably on start-up, particularly compared to PU.