HTHS

[MolaKule]

Three things:

1. Amounts of various viscosities of PAO's to make the XW30, etc.

2. Viscosities of the ester(s).

3. The type and quality of Viscosity Index Improver.

 

[OilAnal]

quote:

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Three things:

1. Amounts of various viscosities of PAO's to make the XW30, etc.

2. Viscosities of the ester(s).

3. The type and quality of Viscosity Index Improver.

---

Thanks, Am I reading too much into this, but it sounds like Mobil1 makes a tradeoff on 1 or more of the above otherwise their HTHS would be higher rather than equal to most dino oils.


BTW. Current Mobil1 1 user using your #132 brew ratios to upgrade this oil at a very slight additonal cost. But the low HTHS bothers me after seeing a SAE report on HTHS importance.

Reference Report- 980702 Properties of Engine Bearings Lubricated with Low HTHS Viscosity Oil. Their cutoff for acceptable wear was 2.6 also.

[ January 05, 2004, 02:13 AM: Message edited by: OilAnal ]

 

[Ken2]

quote:

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Originally posted by TooSlick:
The problem with running thin oils is under high load, low rpm conditions. In this case, you don't develop sufficient oil pressure to prevent intermittant contact of the crankshaft and main/rod bearings. If you tend to lug your engine, don't use thin oils ...

Engines running at high rpms and low loads do just fine with thin oils. Hence, there are sound technical reasons why Acura/Honda can recommend 0w-20 and 5w-20 grades for the bulk of their engines.

Tooslick

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The oil film between the bearing and the journal is created by the rotation of the journal, not by the oil pump. http://www.stiweb.com/appnotes/jb.htm The oil pump just replenishes oil that leaks out of the bearing, carrying heat and dirt away while it leaks out.

Agree, high load and light vis oil is a problem unless the bearing is sized larger to distribute the load over a larger area.


Ken

 

[Titanium_Alloy]

quote:

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Originally posted by MolaKule:
...
HTHS 2.1
mass loss (gm.) - 190

HTHS 3.2
mass loss (gm.) - 28

For "mains" bearings:


HTHS 2.1
mass loss (gm.) - 150

HTHS 3.2
mass loss (gm.) - 40

A jump in HTHS by about +1.5 results in approximately 1/5 the wear. Now this relationship is not linear and flattens as one nears a 40+ weight oil.
...

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MoleKule you indicate wear in gramms. How is it possible to have a 150 grams wear? Are you sure it's not milligrams(mg)?

Regards,

 

[MolaKule]

I will check my references again, but as I recall, this was a highly loaded engine that was run for many hours.

 

[novadude]

Interesting stuff. Has anyone compiled a comparison of HT/HS numbers for current 10W-30 dino oils?

 

[JohnBrowning]

Just so people know you weight the bearings prior to assumble with an analytical scale. THen once the test is done you weight them again.

 

[crossbow]

Hey fella's,

Thought I'd bump this thread back up with a noob question.

I recently saw Terry pointing out some of the redline 5w-20 specs which includes a HTHS of 3.3.

Now I'm a bit confused on this particular notion. If HTHS is more of an indication of true viscosity, why is redline still calling the oil 5w-20? Is this basically a 5w-20 with the flow characterstics of that viscosity, but with an utterly rediculous sheer stability?

With an HTHS of 3.3 it would appear that the oil's nearing some 40 wt's!!!

I guess what I'm asking is if someone could possibly elaborate on the different terminology between the standard viscosity rating (5w-20) and the High Temp High Sheer rating, and how that interrelates.

If this was already answered, please just slap my hand and point me to a thread. =/

 

[MolaKule]

This is a good question.

The viscosities stated at 40C and 100C are an indication of the "Bulk" visocisties of the oil. When the oil is subjected to high shearing and high temperatures such as in bearings and piston ring/liner interfaces, the oil's viscosity could be much lower due to those shearing pressures and heat.

In the most general terms, and especially with the mineral oils, HTHS rises with viscosity.

Now this is not necessarily the case when certain lubricity and AW additives are formulated into a full synthetic or mineral oil. These additives could actually improve the HTHS of the base oil. These lubricity and AW additives BTW, are most generally synthesized hydrocarbons, and synthesized or natural esters.

So a "thin" 5W20 synthetic or mineral could have a real good HTHS.

 

[kenw]

"[Mola's comment: I think this test verifies my earlier comments that most daily driver engines can use any oil from a high quality 5W20 to a 15W40 fleet oil.]"

now, now, we'll have none of this science stuff, we've got snake-oil to sell.....

excellent work. I am so glad to have found this site. Truly refreshing. (altho there are a few snake-oil enthusiasts here...)

 

[moribundman]

From the link MolaKule posted:

quote:

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Lowering the viscosity of engine oil is effective in reducing the fluid friction. However, it decreases the oil film thickness, and causes the increase in the wear of engine parts. Through the engine wear tests using an radioisotope tracer technique, it was clarified that an HTHS viscosity of 2.6 mPa･s was the lower limit to prevent the increasing wear.

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Shooting for the lower limit, are we?

I'd rather prevent the "increasing wear" with a "higher limit." But that's just me.

 

[crossbow]

Thanks for the reply molakule. Let me see if I got this right.

The inital "general" viscosity ratings are just that..."general". They don't take into account areas of the vehicle which may come under excessive heat and/or pressure.

The HTHS # on the other hand, indicates the relative viscosity of the oil when exposed to these situations, such as the bearings used in your example.

Thus someone who routinely bounced off the rev limiter during an autocross, with a close tolerance DOHC V6 spec'in "thin" 5w-20 oil would do well to have one with a relatively high HTHS #

.

 

[MolaKule]

I think you summed it up very well, crossbow.

 

[Arup]

HTHS is also important in HDEO used in low power, highly taxed hard working diesel engines operating under severe heat, typically around 45c temps and going through a cycle of mixed highway and stop and go traffic. Would be reassuring to know that the oil inside your engine is holding up its viscosity under these conditions.

 

[friendly_jacek]

quote:

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Originally posted by MolaKule:

So a "thin" 5W20 synthetic or mineral could have a real good HTHS.

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Interesting statement. Last time I checked, oils with "a real good HTHS", which I define >3.5, are quality XW40 oils, except for the thick-30 GC with HTHS of 3.6.

 

[crossbow]

Ya but you gotta admit...there probably isn't much difference between a 3.3 and 3.5 HTHS...as compared to the differences between a 5w-20 and a 0w-40.

 

[moribundman]

quote:

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Ya but you gotta admit...there probably isn't much difference between a 3.3 and 3.5 HTHS...as compared to the differences between a 5w-20 and a 0w-40.

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Red Line 5W-20 has an HTHS of 3.3.

Volkswagen and Audi found it neccessary to modify the oil system and the cams for those cars that were made to run on low HTHS oil (VW 503.00, HTHS 2.9-3.4). Going by that I would say the difference in performance is not negligible.

 

[crossbow]

Yes...but what if the modifications were to make use of the thinner oil's flow characteristics? Not all modifications are to fix problems

.

 

[moribundman]

I hear those engines use roller lifters, no gear-to-gear meshing, modified oil pumps, and smaller oil passages.

[ October 22, 2004, 03:27 PM: Message edited by: moribundman ]

 

[MolaKule]

I suspect the lubrication circuit's flow rate was increased and the cam/tappet surfaces or bulk metallurgy were hardened.