Highest HTHS Xw-30 Oil?

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Originally Posted By: 92saturnsl2
Originally Posted By: CATERHAM
Invariably when a heavier oil is recommended in another country the climate is hotter and/or the typical driving behaviour is different; i.e., they drive faster. Oil availability is also part of it. The 5W-20 grade is unique to NA.

I respect your knowledge and input on the subject, but is there any doubt in your mind about the US adherence to thinner oils? Is it CAFE oriented, or is it truly in the interest of wear protection? A compromise between the two?
Honestly, I'd sacrifice a smidgen of my fuel economy for the peace of mind knowing the engine will wear less-- Even if the car falls apart before the engine dies.

Asking if it is CAFE motivated is really immaterial, besides GM has not jumped on the 20wt bandwagon yet so one could argue that GM hasn't made any compromizes unlike Ford, Toyota and Honda et al who may have.
All you want to know is the optimum viscosity for your application. Since you're fortunate to have a OP gauge in your car that makes it very easy to determine. I guessed that the minimum OP spec' at elevated rev's for your GM engine is 50 psi.
(you can look it up to confirm and there is also a spec on idle to compare to). As long as you maintain that minimum OP there is zero benefit to running a heavier oil. Since the spec' oil is a light 5W-30 you will find you're running with a very large OP safety margin indeed.
 
I don't want to argue back and forth with the experts here who abide by "Dr. Haas' Motor Oil 101 article" in the articles section, but there are two false teachings in that article:

(1) Unlike claimed in that article, synthetic oils do not have any magic properties and they do not provide additional wear protection. They are simply made from better basestocks but this doesn't translate into better wear protection. Better basestocks withstand colder and hotter temperatures more than dino basestocks but that's about it. You might benefit from longer OCIs with synthetics as their basestocks are more robust but that's not necessarily always the case either. In fact the most popular synthetic oil, which is probably the only true (PAO-based) synthetic major-brand oil -- Mobil 1 -- fails to even meet the GF-4 wear-protection standards and is worse than any major-brand dino oil in that respect. The reason is possibly lack of viscosity modifiers, which thicken the oil film at high shear. (Note: GF-5 Mobil 1 has just arrived in the stores and they may have changed the formulation, having more VIIs for better wear protection.)

(2) "Dr. Haas" article claims that thickness of the oil film has no effect on engine protection. This is the biggest fallacy of this article and has mislead many people on this forum. See the ASTM paper linked above regarding the direct relation between oil-film thickness and wear protection. "Dr. Haas" claims that oil is incompressible and therefore film thickness doesn't matter. While oil is incompressible, it's not unsqueezable and oil-film thickness does matter. Physics of wear is quite complicated and oil-film thickness plays the biggest role along with the antiwear compounds.

Falling into the fallacy of disregarding the oil-film thickness, "Dr. Haas" then concludes that the only thing that matters is the oil flow. Therefore, he calculates oil pressure for various viscosities and concludes that for most cases the thinnest viscosity is the answer because it provides the best flow.

So, no, "Dr. Haas" is wrong and oil-film thickness, which is primarily determined by the HTHS viscosity and the amount of VIIs (more HTHS vis or more VIIs, thicker the oil film at high temperatures), matters for engine wear.

Does that mean that you should use a multigrade oil with the highest HTHS vis? Not necessarily. Modern engines wear very little in most driving conditions even with the thinnest oils as their geometries and dynamics are designed not to wear much. So, you may not see a significant benefit from using a thicker oil, especially if you're not going to keep your car for more than 100,000 or even 200,000 miles. Many other things start breaking much sooner than the engine. Also, the fuel economy directly relates to HTHS vis. and the difference between fuel economy for 0W-20 and 20W-50 is around a whopping 15%. (There is also a chance that very thick oils, such as 20W-50, may cause problems [oil pump, VVT-i systems, etc.] in certain cars designed for the thinnest oils.)

A good dino 5W-20 or 5W-30 may be sufficient for most modern engines in more or less normal driving conditions. Hard-driven cars (uphill, high-speed, fast acceleration, prolonged idling, towing, engine lugging, very high operating temperatures, etc.), especially older designs, would likely benefit from 5W-40. Yet even older cars could benefit from 15W-40, which has higher HTHS vis than 5W-40. And 20W-50 could be good for really old cars that wear quickly or for certain race-car engines.
 
Originally Posted By: Gokhan

...

(2) "Dr. Haas" article claims that thickness of the oil film has no effect on engine protection. This is the biggest fallacy of this article and has mislead many people on this forum. See the ASTM paper linked above regarding the direct relation between oil-film thickness and wear protection. "Dr. Haas" claims that oil is incompressible and therefore film thickness doesn't matter. While oil is incompressible, it's not unsqueezable and oil-film thickness does matter. Physics of wear is quite complicated and oil-film thickness plays the biggest role along with the antiwear compounds.

Falling into the fallacy of disregarding the oil-film thickness, "Dr. Haas" then concludes that the only thing that matters is the oil flow. Therefore, he calculates oil pressure for various viscosities and concludes that for most cases the thinnest viscosity is the answer because it provides the best flow.

So, no, "Dr. Haas" is wrong and oil-film thickness, which is primarily determined by the HTHS viscosity and the amount of VIIs (more HTHS vis or more VIIs, thicker the oil film at high temperatures), matters for engine wear.

...



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If the OP has added the blower, or has increased boost pressure above stock levels, the manufacturer's oil recommendation may not be sufficient. IMO, there's no reason to stick with Xw-30, although GC and M1HM both offer ~3.6 hths. If he's really leaning on the engine, I'd suggest he look for even more HTHS.
 
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^Gokhan...and yet, 'too thick' could result in harder work for other parts of the engine, like the rods and shafts that get the brunt of any overkill in 'pressure' from an insane choice of oil grade, if primarily for HTHS or not.

Also, wouldn't it be important to know WHAT additive in any given oil or formulation is doing the grunt work in the oil film 'strength'(not thickness necessarily); if there is a quality difference?

Your speculation for grade jumping is assuming the vehicle can't maintain proper oil pressure and make power without knocking/pinging etc, and while a thicker weight could masks or perhaps help in certain apps, it's quite another thing to just go for the highest or most 'likable' HTHS oil when there is so much more to it than that. If both 5w-30 and 5w-40/15w-40 produce the same 'wear rates' among metals where film strength is achieved(not film thickness dependent per se), then why would going thicker help if you aren't doing extreme driving(not severe service mind you) if the engine has to work harder/longer to crank or perhaps is now working harder to overcome the higher oil pressure in the system(higher isn't always better)?

Could that be a trade off for certain wear to another?
 
^I would like to add, in the context on HDEO I definitely believe the HTHS is more advisable than any thoughts on 'film-strength' as a means to say a lower grade is 'adequate'. I believe Dr. Haas was simply going over some basics, in particular motor oil in a passenger car/truck, not necessarily along the lines on diesel or HD gas apps.
 
Originally Posted By: CATERHAM
Asking if it is CAFE motivated is really immaterial, besides GM has not jumped on the 20wt bandwagon yet so one could argue that GM hasn't made any compromizes unlike Ford, Toyota and Honda et al who may have.


Not yet anyway. I predict that GM will be spec'ing xw20's to meet CAFE standards over the next few years.
 
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.
 
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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.
 
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.


UOA's are not a tool for measuring "wear". They are for monitoring contamination and oil life.

Redline is also noted for chemical chelation, which will show as increased "wear" metals in a UOA, but is not actually "wear".
 
Without getting into the argument of moving up to Xw40, here's the highest HTHS I've ever seen on an Xw30:


Torco SR5 5w30: 3.7
Motul 300V 5w30: 3.61
Castrol Syntec 0w30: 3.6? (rumored, it's definitely 3.5 or better)
Mobil 1 HM 10w30: 3.6


I actually just switched to the 300V 5w30 (from 5w40) because it still has HTHS above 3.5 per my manufacturer requirement. I'd have gone for the Torco but the TBN is like 5.2 because it's a race oil.
 
Originally Posted By: INDYMAC
Lubrication Engineers makes a 10W-30 SM/CJ-4 engine oil with an HTHS of 3.7. It's called Monolec Ultra-Blend #8130. This is a very well formulated HDEO that works well in gas engines too.


Shell Rotella, Triple Protection, 10w30 also comes in a conventional oil and is readily available for a good price. I'm using it now with a mix of Formual Shell 5w30 in a gasoline engine.
 
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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.
 
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.

Actually I was basing that last statement on an ASTM research paper. See Page 50, Figure 4. It shows that HTHS viscosity being equal, multigrade oils have thicker oil film at high shear (high RPM) and single-grade oils have thicker oil film at low shear (low RPM).

My explanation for this is that at high-shear conditions, viscosity-index improvers (VIIs) increase the oil-film thickness by working on the high-shear areas. At low-shear conditions, VIIs are not operating in the maximum level and you see a reduction in oil-film thickness.

Many people view VIIs as a purely bad thing (other than improving the viscosity index) because they may eventually tend to shear. But apparently they are also important to increase oil-film thickness at high shear (HTHS viscosity being equal) and they are also a good thing. In fact, the reason why Mobil 1 performs worse in wear protection than most other oils could be that it's PAO-based and shows a lack of VIIs.
 
I'm quite familiar with James Spearot and referenced him in my piece "HTHS vis trumps KV100".
I will point out that paper is over 20 years oil and is comparing mineral oils with and without VII's.
Today virtually all multi-grade oils contain VIIs and the only ones that don't are very expensive GP IV & V based oils so the point you're making is redundant.

Your leap claiming that M1's higher wear rates [of some grades] is due to their PAO chemistry and lack of VIIs shows a lack of familiarity with their products.
Most if not all of their oils contain VIIs and they use many different base oils including GP III and ANs.
 
Originally Posted By: wlyszkow
Take a look here please and tell me which oil (which HTHS is better?) for this Subaru and its bearings (~5 on the left or ~4 on the right):
http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=228343

;-))

Interesting comparison. Here is the original link.

He was racing with these two oils. It's very hard to do a meaningful UOA comparison when you're revving your engine to near death, especially considering that they were two different race tracks. Moreover, it's also possible that, after the first race, the bearings were broken in, which resulted in less wear in the second race.
 
Originally Posted By: wlyszkow
Take a look here please and tell me which oil (which HTHS is better?) for this Subaru and its bearings (~5 on the left or ~4 on the right):
http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=228343
;-))

A comparison of a heavy oil (AMO 10W-40 HTHS 4.3cP) and a very heavy oil (20W-50 HTHS 5.0cP).
Of course a single UOA each is anything but conclusive, but to quote Doug Hillary, an admitted heavy oil guy, "a HTHS vis higher than 4.2cP tends to become counterproductive (refer to ACEA protocols and Motul's comments) unless fuel dilution is relevant or a "special" app' demands it."
 
There's a lot of good discussion in that paper, and I agree with what it says about higher viscosity increasing oil temperature. You may pour an oil with twice the viscosity into your crankcase, but because that oil runs hotter in the bearing, it will not have twice the viscosity where it really counts.
 
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