Highest HTHS Xw-30 Oil?

[Gokhan]

I think in most of the modern engines, the cooling system does most of the work and you wouldn't see a significant difference in engine temperatures because of the viscosity of the oil. Also, when the temperature rises, viscosity falls, and any such effect has negative feedback on itself, making it even less significant.

The situation could be different in extreme conditions and racing.

 

[wlyszkow]

Yes, but in my opinion increasing bearings' working temp is not healthy, isn't it?

 

[Gokhan]

It wouldn't be healthy to run above the normal-operating temperature. The question is how much the oil viscosity affects the bearing temperatures. Perhaps someone knows. My guess is that since there is good thermal contact with the bearings, the rest of the engine, and the cooling system, I doubt you would see a significant increase in temperature due to increase in oil friction. I am sure the bearing temperature for various viscosities were studied somewhere and it would be nice to see those studies.

 

[engineerscott]

Originally Posted By: HondaMan
Originally Posted By: 92saturnsl2
Does anyone know off hand which oil has the highest HTHS value, of the 30 weights? Correct me if I'm wrong, but I think that specification would be beneficial in a supercharged engine (GM 3800) that is often driven aggressively.

I've noticed that the thicker GC 0w-30 I'm using now maintains oil pressure better (doesn't drop below half on the oil pressure gauge, 40 psi) when hot, compared to lighter oils such as PZ Ultra 5w-30, which often go down to 3/8 on the gauge. Whether that has any bearing (no pun intended on protection or not, I'm unsure.

Would a thicker oil be of any benefit in this application? Perhaps something like M1 0w-40 or along those lines?


I tried this with my Silverado , I opted for Redline, very high HTHS and very thin.

Combination did not work. ... the approach of picking out a value such as HTHS and selecting based upon that one value is not sound I have learned.
Oil held up great, UOA wear was terrible with PYB showing better wear protection.

BTW, if you do go with a pure numbers approach, again Redline will have most of the best oils on paper in this regard.


Which Redline oil were you using and what were the results that lead you to conclude that the "combination did not work"? Just curious.

 

[OVERKILL]

Originally Posted By: engineerscott
Originally Posted By: HondaMan
Originally Posted By: 92saturnsl2
Does anyone know off hand which oil has the highest HTHS value, of the 30 weights? Correct me if I'm wrong, but I think that specification would be beneficial in a supercharged engine (GM 3800) that is often driven aggressively.

I've noticed that the thicker GC 0w-30 I'm using now maintains oil pressure better (doesn't drop below half on the oil pressure gauge, 40 psi) when hot, compared to lighter oils such as PZ Ultra 5w-30, which often go down to 3/8 on the gauge. Whether that has any bearing (no pun intended on protection or not, I'm unsure.

Would a thicker oil be of any benefit in this application? Perhaps something like M1 0w-40 or along those lines?


I tried this with my Silverado , I opted for Redline, very high HTHS and very thin.

Combination did not work. ... the approach of picking out a value such as HTHS and selecting based upon that one value is not sound I have learned.
Oil held up great, UOA wear was terrible with PYB showing better wear protection.

BTW, if you do go with a pure numbers approach, again Redline will have most of the best oils on paper in this regard.


Which Redline oil were you using and what were the results that lead you to conclude that the "combination did not work"? Just curious.



It's a red herring regardless. UOA's are not a "wear determination" tool. Contrasting minute PPM variances between oil brands is the ultimate exercise in futility.

 

[engineerscott]

Originally Posted By: OVERK1LL
It's a red herring regardless. UOA's are not a "wear determination" tool. Contrasting minute PPM variances between oil brands is the ultimate exercise in futility.


I certainly agree, but it wasn't clear to me that UOA wear metals where the reason he decided he didn't like Redline. I'm just curious to hear his reasoning.

 

[OVERKILL]

Originally Posted By: engineerscott
Originally Posted By: OVERK1LL
It's a red herring regardless. UOA's are not a "wear determination" tool. Contrasting minute PPM variances between oil brands is the ultimate exercise in futility.


I certainly agree, but it wasn't clear to me that UOA wear metals where the reason he decided he didn't like Redline. I'm just curious to hear his reasoning.



I suppose I'm curious as well, red herring and all, LOL

 

[fpracha]

Originally Posted By: CATERHAM
Originally Posted By: 92saturnsl2
Why do vehicle manufacturers specify thicker grades of oils in other countries for the same vehicle if there is a disadvantage to it as you suggested?
A lot of vehicles sold in other countries recommend a 5w-40 or equivalent for vehicles that specify 5w-20 or 5w-30 here. I'm not drawing any conclusions based on that fact, just asking the question why.

Invariably when a heavier oil is recommended in another country the climate is hotter and/or the typical driving behavior is different; i.e., they drive faster. Oil availability is also part of it. The 5W-20 grade is unique to NA.
By "driving faster" , do you imply hard acceleration and include short bursts of acceleration & deceleration OR are you implying high speeds when saying "driving faster" ?
What is hotter climate... >70F ambient or >90F ambient temperatures?
(ps: Gokhan here appears to be using 5W-20 in an old Toyota engine (1985) with lots of miles on it (241k mi), even in the hotter California climate!)

 

[fpracha]

Originally Posted By: CATERHAM
Originally Posted By: Gokhan
Looking for an xW-30 with high HTHS viscosity is quite contradictory.

If you need high HTHS viscosity, use xW-40 or xW-50. HTHS viscosity is much more important than the 100 C kinematic viscosity, as that's what determines fuel economy (negatively correlated) and oil-film thickness (positively correlated), not the 100 C kinematic viscosity.

Also, if you're concerned with oil-film thickness, consider a dino oil instead of synthetic. Dino oils usually have more VIIs than synthetics, and for a given HTHS-viscosity number, more the VIIs you have, thicker the oil film.

You're first two sentences are correct but your last statement is not.
Yes synthetics have less VIIs than dinos for a given HTHS viscosity but that's an advantage for many reasons not a disadvantage. If two oils have the same HTHS vis' they have the same film strengh (at 150C) regardless of their VII content.
+1. and anyway, if HTHS is same for two oils (dino or synthetic), oil thickness will be same for these two oils regardless of dino or synthetic. Even if more VIIs are in the oil, the HTHS is the guideline to go by.

 

[Shannow]

Originally Posted By: Gokhan
It wouldn't be healthy to run above the normal-operating temperature. The question is how much the oil viscosity affects the bearing temperatures. Perhaps someone knows. My guess is that since there is good thermal contact with the bearings, the rest of the engine, and the cooling system, I doubt you would see a significant increase in temperature due to increase in oil friction. I am sure the bearing temperature for various viscosities were studied somewhere and it would be nice to see those studies.


Bearing design is a circular argument.

You start with a design input temperature, and a desired outflow temperature, and a known rate of shear, plus some side leakage parameters based on the average viscosity (inlet versus leakage).

That gives you a frictional loss for that bearing, which then thermodynamically gives you a new outlet temperature, which gives you a new operating viscosity...which gives you a frictional loss and a new outlet temperature.

Round and round, and repeated for every bearing in the machine, to get a suitable design.

Each bearing will heat the oil to a greater or lesser degree, which not only affects HTHS, but oxidation, varnish production and ultimately oil life.

I've shaved 18" bearings 0.5 to 4 thousandths of an inch to get the clearances right, to get the operational viscosity right, and to avoid singularly excessive local temperatures.

 

[Fyrb4ll]

Originally Posted By: CATERHAM
The 5W-20 grade is unique to NA.


And gee, strangely enough so are CAFE standards. Hmmmmmm.......

Good grief, enough of the KoolAid.