"Engine oil viscosity has VIRTUALLY NO EFFECT ON WEAR."

[Ugly3]

Gary Allen - no one appears to have wanted to bring this matter into discovery. No research ..or rather all research stops before attempting to figure this out. Conspicously so.

Any thoughts on why this is the case? Maybe very very difficult to do but I would think some University would undertake the task.

 

[buster]

You would think by now that all of this stuff would be understood, but as Motorbike just posted in this thread, so much is still not known.

Shell article on Viscosity posted from Motorbike

I think this is a safe betb]

From Terry:

Vis in a engine is like shoes on the feet, too tight and it rubs you sore, too loose and you slop around all over the place

MATCH the right viscosity with the engine. Do an analysis and let that tell you. If your getting great wear in a Toyota or Honda with a thin economy oil, let it be. Why go up in viscosity to rob HP and increase heat for no reason? That is one thing I never understood with those that move to a thicker oil even though a thinner oil is doing it's job.

[ January 24, 2005, 05:46 PM: Message edited by: buster ]

 

[MolaKule]

The engineer has to determine:

1. At what temp will wear occur and on what component?

2. What is the minimum viscosity at which wear starts accelerating?

3. How do the additives affect the overall viscosity and wear properties/requirements of the engine/oil combination.

 

[Dr. T]

You can't specify a proper or minimum HT/HS for a specific engine because (under non-BS conditions) an engine can tolerate a wide varied viscosity range.

For eg. my 1994 BMW specifies any oil from a 5-20 to a 20W-50 depending on ambient temperature. Do you think these two oils have different HT/HS's??? Sure. But, that fact doesn't matter as much as at what temperature range the said lubricant is being utilized.

Granted, the viscosity chart was created for conventional oils, but I still think that it still holds true for synthetics (although maybe on a loser scale).

 

[Ugly3]

The part that confounds me is that in Europe such thick oils are recommended and in the States such thin oils are recommended. One might think that wear and engine life are not on the top of the agenda.

 

[darryld13]

quote:

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Originally posted by Ugly3:
The part that confounds me is that in Europe such thick oils are recommended and in the States such thin oils are recommended. One might think that wear and engine life are not on the top of the agenda.

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With Volvos and Mercedes collecting multiple 250K mile badges in the US, maybe they know something regarding a need for different recommendations in the US vice Europe?

 

[Dr. T]

Cars are generally less maintained in Europe. Many US owners subscribe to 3k OCI's...driven at 55 mph, they could last forever...

 

[Gary Allan]

quote:

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Some of the films also seem to get generated under specific conditions and have different durability. The net result seems to be that the films generated, some desired and others not, act like storage capacitors for some metals, and fresh oil seems to disrupt some of the films. That's why people observe 'old oil produces less wear than fresh oil' when observed with either used oil analysis or trace analysis.

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So ..is it your suggestion that new oil (any new oil) has some component that aggressively seeks to form its own protective film ...thereby displacing the existing film barrier...and that the formation or completion of that process coincidentally appears to fall into 2-3k of any oil's life? I mean that would fit the symptoms of the upramp in wear metals in this range ..and how they stabilize from that point on ..gaining as "normal" metal ejecta is added to the mix???

We could however ..just spin that around to say that the protective films entrain metals in their formation and that indeed the upramp is the resuspension of residuals that are precipitated out from the last OCI. There would be no apparent difference if the particles came from non-protective film precipitation ..or from disturbed "bonded" particles being exchanged for new protective film formation.

So from a metal content analysis view (assuming that we are going to interpret the presense of metals as indicators of wear) we could all have no indicated wear by just changing oil before these protective films are disturbed.

or spun another way around..


Anyone who does a 3k OCI is just about reaching the point of the complete formation of a protective film (displacing the old one) ...and then flush it all down the drain ????

 

[Gary Allan]

quote:

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I don't know the answer but to see decisions made on the basis of wear metals in a used oil analysis is at best based on an undocumented assumption.

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I would rather term it a highly documented assumption. Istruck and I went around on this and figured out that although many have speculated about it ..no one appears to have wanted to bring this matter into discovery. No research ..or rather all research stops before attempting to figure this out. Conspicously so.

I would like to point out ...that virtually all of the break-in used oil analysis have highly elevated metal content. This, at least, suggests that there is some correlation between metal ejecta and used oil analysis indications.

The long way around to a non-conclusion.

 

[1sttruck]

As mentioned in the 'long thread', if you're interested in measuring wear then you need to use a technique that reliably measures wear. Wear metals in a used oil analysis is just a measure of metals suspended in the oil, and it's a bit of an assumption to think that it indicates wear. A key point is the observation that 'fresh oil creates more wear', as suggested by higher wear metals in a used oil analysis or trace analysis. That observation needs to be tempered by the other studies where wear is actually measured, which suggest that used oil needs to be used for wear studies because it creates so much more wear, and that something like adding abrasives to fresh oil needs to be standardized for wear studies.

I'm guessing that the volatiles in the fresh oil, or the solubility of some base oils, disrupts the anti-wear and other films, and that's why you tend to see 'more wear as indicated by higher metals' in used oil analysis. More data on the structure and properties of anti-wear and other films is needed for our questions.

 

[Dr. T]

I completely agree. A used oil analysis only displays the elemental wear that's suspended in the oil. What happened to the wear elements left behind as sludge, carbon or varnish? What about burn-off?

 

[lobo11]

If some of you guys want to read some really intersting work on boundry lubrication check out some of the Ultrathin Film Interferometry work being done by Hugh Spikes at the Imperial College of Science in London. His article--Direct Observation of Boundry Layers will shed a lot of light on the above arguments, and is an easy read.

 

[lobo11]

Try this link for the afore mentioned article. The author has multiple works in this area.
http://pubs.acs.org/journals/query/subscriberResults.jsp

 

[lobo11]

**** , that didn't work--regardles try going to the ACS website above and searching by author--remember to change the date of search as it defaults to only 4 years back. Sorry about the inconvienence, but it is worth the time it takes--an excellent read regardless with some interesting information on viscosity behavior in the "boundry layer" itself.

 

[Terry]

struck and T, using the total analysis report compared/correlated to data base of known signatures for the engine and lubes is the way you do that. Experience of the analyst has a lot to do with the accuracy too.

T, the question you ask in the last post is why the physical properties of the oil are tested.

I look at the whole result, use feedback from the customer and compare that to what I have seen for years to get a good measure of the engine and oil condition.

The ability to provide a repeatable automatic value of wear and remaining life in one test without the subjective input from a analyst just doesn't exist , yet. Cost and demand is the limiting factor.

I am trying to develop a test "package" that would provide more than the the current used oil analysis you are concerned about. Problem is I don't think very many would pay the $100's of dollars to use it.

The ability to GCmassspec work for less than $1500 a run is a start.

 

[TallPaul]

Ok, just found another HTHS statement by Callisa (from Noria) in response to my statement.

quote:

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Originally posted by Callisa:

quote:

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It seems to me that, since HTHS is a measure of viscosity, one would want it to be within a reasonable range, not too high, not too low.

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HTHS is a _virtual dynamic_ viscosity at 150°C and a shear rate of 20 m/sec. It was "invented" due to the fact at the beginning of the 80's engines failed with oil of an HTHS < 2,0.
During a SAE congress in the 80's, all members agreed, that the available data showed that an HTHS > 2,5 is fair enough for every engine on the market in those days.
High HTHS values give you a fuel penalty. Depending on your engine, you will experience a higher fuel consumption of 2% if you use an oil with HTHS of 5 instead of 2,9.
Either your engine is durable, or it is not. If it is durable, high HTHS values don't give you a "safety margin". Thats especially true for your normal car, and that's also true for Diesel engines.

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[buster]

People can say what they want, like Dr.T, but results like these tell the tale.

http://theoildrop.server101.com/cgi/ultimatebb.cgi?ubb=get_topic&f=3&t=002254#000004

 

[Dr. T]

buster, you can say what you want too because it's an open forum..and we're all supposed to be learning. But, since you already know everything then we should all be using a 20weight. Your link points to a decent UOA using 5-20 in a 40k mi. Honda Civic. So what? What happens at 200, 300, 400k mi.?

My experience: Brother's 120k mi. 92 Civic did not pass emissions using Mobil 1 5w30 every 3-5k last year. Guess he should have used the 0-20....what a retard.

 

[buster]

quote:

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buster, you can say what you want too because it's an open forum..and we're all supposed to be learning. But, since you already know everything then we should all be using a 20weight. Your link points to a decent UOA using 5-20 in a 40k mi. Honda Civic. So what? What happens at 200, 300, 400k mi.?

My experience: Brother's 120k mi. 92 Civic did not pass emissions using Mobil 1 5w30 every 3-5k last year. Guess he should have used the 0-20....what a retard.

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Dr.T, I know no more than anyone esle on here but you my friend, constantly ignore and distort the truth regarding viscosity. Hanv't you learned by now that the used oil analysis for the 20wt oils are very good? Aren't you also aware that modern additives play a role in oil too, not just the viscosity of the oil? I don't think everyone should be running a 20wt oil. I think you should run the lowest viscosity that gives you the best wear, HP and efficiency.

When cars age, you'll eventually have to step up to a thicker oil. If oil analysis says your getting great wear protection compared to a thicker oil, then what purpose does it serve to use a thicker oil? Why create more heat, less HP and lower efficiency over all using a thicker oil when the thinner oil will do the job better? You have to match the engine withe the correct viscosity. You can't just preach using thicker oils when they are NOT always needed, as are the 20wts. It's ridiculous. And BTW, if that Civic wasn't burning any of the 20wt off, their would be no problem. If I had a car that was consuming a X-20 oil, I'd move up a grade, otherwise your fine running the 20wt oil.

I don't push 20wt oils where they don't do well. For instance an LS1. We've seen that engine likes a 12cSt oil or higher. But in a vehicle that shows low wear and no oil consumption, a 20wt oil would be fine. For racing, step up to a light 30wt maybe. It all depends....

[ January 29, 2005, 11:56 AM: Message edited by: buster ]

 

[Dr. T]

Great, so if there are no bad 0-20 used oil analysis, then we should all be using it and the new Castrol R should be 0-20, not 0-40...what were they thinking?

The probable truth is that there is a difference...we're just still looking for it. But, no manuf. outside of N.A. specs a 20 weight oil. Any oil will get you to 100k and the funny thing is the used oil analysis will show you everything's fine.

To each his/her own....my experience has shown otherwise. You can choose to increase viscosity AFTER your engine is worn. I prefer to prevent wear before this happens...also something a used oil analysis won't show you.