*Oil Analysis - interesting post

[buster]

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[Caveat]Without knowing much about automotive oils technology, but being a practicing chemist, I will try to offer an opinion. [/]

Oil technology is stupidly proprietary and ultra top secret, so there's practically no real research in the academic or government realm--most of the research is highly empirical, meaning its conclusions can NOT be generalized outside of the testing regime chosen. While a self-educating person of knowledge can learn a thing or a lot about what an additive "does", he can not know how that additive will behave in a different environment or in differing proportions to other additives.

So here are some basics: most transition (d-block) metals such as zinc will only dissolve to a very tiny fraction in oils, typically ppm or less; therefore to get an effective proportion of them into the oil, you must chelate them or form an organometallic complex with a ligand molecule, which itself has a high solubility in your oil's base stock.

Traditional chelators tend to be more non-specific and will chelate many metals, including contaminant metals from the process tanks and piping and solders where the oil was refined.

Ligands are generally more tailor-made molecules that will form stable complexes with only certain metals of a given ionic radius range. They are more expensive.

Lability refers to a chelator's or ligand's ability to give up its metal center, or how tightly it holds onto its metal under a given set of conditions. Chelators generally have less lability and are harder to chemically "tune" whereas ligands generally have greater lability and are more tunable. You can tune a ligand to be heat labile or pressure labile so that it will release its metal center above a critical heat/pressure threshold. When the metals are released, they will 'plate out' in the micro voids that they typically find themselves in during those high temperature/high pressure events. Below that temperature/pressure threshold, the metals will be slowly recomplexed by their ligand or chelator. Plating out (reducing)is a spontaneous phenomena for many metals and depends on the net electrochemical potential (standard reduction potential, in volts) between the ionized (freely released from chelator or ligand) species and the steel. Plating out (reducing) is also temperature/pressure dependent but that is way too complex a phenomena to discuss.

I am not exactly sure how the specific protection of metals is afforded, but I believe it is the plated out metal that protects the engine parts because these metals are much softer than steels and will deform to take up stresses, thereby protecting the steel parts themselves from direct contact. There may be more nuance to it than that; this is my simplified understanding only.

Highly tuned labile ligands are much more expensive in R & D development costs. Moreover, they are generally more expensive to produce and manufacture. As you can imagine, their identity, composition, lability, Tcrit and Pcrit are ultra-double-death-by-toenail-extraction-top-secret.

This means that two oils, having the exact same ppm's of metals, can behave in dramatically different fashion, due to the ligand/chelator profile and how they are tuned.

Simply looking at ppm of metals in an engine oil will tell you next to nothing about how that oil will perform in this day and age. In prior days when the choices and technology was limited, most oil manufacturers used the same chelators and classes of chelators. No one had any significant advantage and all had to use roughly proportional metals profiles to achieve a given level of protection. Back in that time, simple analysis of the metals profiles could give you a very rough idea of how it would perform relative to another oil having a different "additive" profile. But in this day and age, the technology of ligands is so advanced that a glance at an oil's metals profile will only serve to mislead you!

Given their high R & D and production costs, their exact nature, formulation, and activation pressures/temperatures makes these ligands so highly classified that NO ONE of us outside of that research lab is going to be able to have the faintest clue of its performance in the real world. We are limited to an ad hoc empirical approach--which means you can not usefully generalize the results of one study to another application.

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Found this on the TDI forums. Redline? Dave talks of something very similar.

 

[Dad2leia]

Holy #@$%! batman....it really IS rocket science!!!

Still, though, given all of the different combinations of those chelators, ligands, and labiliters, one would think that the oil manufactures could divulge the ppm of the various elemental items in their formulation..without having to get a VOA done at our expense.

 

[bruce381]

I'd say he more wrong about most of that than right
bruce

 

[N2OIL]

Interesting about oil & metals have no relationship of each other. I guess every 100 hours most turbine operators just waste money to have a sample done then.

 

[buster]

I don't fully agree with this guy. He is honest and said he's not an oil expert, just a chemist but I've always questioned some of the oil analysis results in terms of engine wear.

 

[Jaybird]

I am but a lowly curious george and student of tribology...but from my studies, this fellow has it nailed spot-on.
Sacraficial mechanisms immediately come to my thick head.

I don't think the author was saying that elemental ppm #s are worthless, just that they may not indicate what conventional wisdom thinks they do.
And he did a fair job of explaining it to us laymen.

 

[WishIhadatruck]

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I don't fully agree with this guy. He is honest and said he's not an oil expert, just a chemist but I've always questioned some of the oil analysis results in terms of engine wear.

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The way I read what he's saying is that the Virgin OA is not that helpful to predict performance. I don't think he was even talking about used oil analysis. I have no clue if he's right or wrong however.

 

[Craig in Canada]

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Interesting about oil & metals have no relationship of each other. I guess every 100 hours most turbine operators just waste money to have a sample done then.

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I think the authour is claiming that determining oil properties from a *VOA* is of little value, since all the forms of, say, zinc may not be properly represented.

Nowhere do I see the claim that testing for WEAR metals in used oil has no value.

 

[buster]

 

[Steve S]

Sounds like internet b.s.to me. Although I am sure the testing of the additive packages is expensive.

 

[farqyj]

That opening post embodies much of what as used oil analysis interpreter, I try to explain to customers. Just because you have Xppm of Zinc, does not mean you are getting X amount of protection. There is a common misrepresentation that ppm of additive metals is equivalent to amount of protection. Obviously there is organic molecules, which are added, and get lost in the carbon soup of oil, that act in conjunction with those metals. I mean, when they say that oil gets oxidized, waxed or varnished, there is no reference to the additive metals changing, but the oil and especially the additives themselves. Keep in mind that blended oils like 15w40 and 5w30 have piles of Viscosity Improver in there that is designed to keep the viscosity high at high temps and low at low temps, but that molecule is very prone to cleavage and oxidation.

It is why you cannot just add more additives and keep driving: you need to change your oil every now and then...