Article on bearing life from Machinary Lubrication

[Primus]

May be I have not catch everything in this article, but it looks like an explanation (please correct me, if I'm wrong) why many oil manufacturers claim now that the last generation Gr.III oils (in fact the same mineral oils, just purified) are equal or better than Gr.IV oils in number of applications:

http://www.machinerylubrication.com/article_detail.asp?articleid=661

 

[Dan4510]

The tests shown in the article do no represent loads on engines. Bearings in gas and diesel engines are not of the caged roller bearing type, nor are they of the twin disk type used for testing. From what I understand, these are used in large industrial engine type settings.

It would not seem to translate that well to auto engine operation.

Dan

 

[tom slick]

quote:

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Originally posted by Dan4510:
The tests shown in the article do no represent loads on engines. Bearings in gas and diesel engines are not of the caged roller bearing type, nor are they of the twin disk type used for testing. From what I understand, these are used in large industrial engine type settings.

It would not seem to translate that well to auto engine operation.

Dan

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that's probably why it's on a machinery lubrication page.

 

[Jay]

Dan, many engines run on roller or ball bearings. Almost all dirt-bike engines, 2-stroke and 4-stroke, run on roller, ball, or needle bearings; but the EHD regime occurs with plain bearings also. Oil has to go through the EHD regime before barrier lubrication takes over. Cams and cam followers, roller and slider, experience EHD lubrication.

That was an interesting article, Primus. Cycloaliphatic hydrocarbons are group III?

 

[buster]

Molekule hopefully can chime in on this. No idea...

 

[MolaKule]

quote:

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Cycloaliphatic hydrocarbons are group III?

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I don't think the article is referring to Group III oils when discussing cycloaliphatics.

I think the article is discussing "Multiply Alkylated Cyclopentanes" (or Cylclopentadienes) which have 20 or more carbon atoms and of which tris(2-octyldecyl)cyclopentane is one. Tris(2-octyldecyl)cyclopentane is also known as Pennzane Synthsized Hydrocarbon Fluid X2000, VI = 136 and PP of -58 C. You know it as the "Pennzane" molecule.

The only other cycloaliphatics known for lubrication properties are the hydrogenated alkybenzenes.

There are 400+ cycloaliphatics, and since the article was not specific, I have to assume the article is talking about the cyclopentane groups, which are the only ones to date that have been commercialized in any real quantity.

 

[Primus]

Sorry not to be very clear from the beginning, but I had not in mind Cycloaliphatic Hydrocarbon. It's a new name for me. But the second after Cycloaliphatic Hydrocarbon was Paraffinic Mineral Oil. This was already a surprise to me.

Gr.III keeps advantages of natural properties of mineral oil, but all weak sides are corrected and became close to the properties of PAO after the treatment.

 

[MolaKule]

BTW,

Don't confuse the Cycloaliphatic series with Alkylated (Benzenes and Naphthalenes) series.

They are two different familes.

 

[Jay]

Thanks for the clarification, Primus, Molakule. The article seems to conflict with what we have heard from various synthetic oil makers about film strength. Amsoil, for example, has said synthetic oil has 10 times the film strength of mineral. This article seems to contradict this, or is "interfacial film thickness" different from film strength?

 

[MolaKule]

quote:

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4. Santotrac Synthetic Traction Lubricants Bulletin. Findett Corporation, St. Charles, Mo.

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Also realize the guy who wrote the article makes these high traction fluids.

In the EHD regime of lubrication, the shear and contact stress for small areas such as ball bearings is significant.

BTW, cycloaliphatic hydrocarbons are synthesized hydrocarbons, thus can carry the "synthetic" or Group V designation.

 

[oilyriser]

Wouldn't a polyalkylated naphthalene have a similar shape to a polyalkylated cyclopentane? It would be a bit wider, but still basically a ball with a bunch of arms sticking out. Would it also have a high traction coefficient?

Would a low traction coefficient lube give the lowest friction in the piston ring area?

 

[cryptokid]

lubes and greases quoted chevron and some other companies that g3 is just as good or better then g4 for alot of auto apps.

if i can find he article ill quote it in its entirely.

 

[MolaKule]

quote:

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Wouldn't a polyalkylated naphthalene have a similar shape to a polyalkylated cyclopentane? It would be a bit wider, but still basically a ball with a bunch of arms sticking out. Would it also have a high traction coefficient?

Would a low traction coefficient lube give the lowest friction in the piston ring area?

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The structures between the two are quite different and are mainly seen their respective rings, the number of "fuseable" rings, and their CHx intervening bonds.

Both fluids can be made to produce high traction types.