Oil Wear Testing and Ranking 1

[LionelHutz]

Anyone care to comment on this oil blog?

http://540ratblog.wordpress.com/

I'm curious what some of the experts here think of this. His big claim is that his undisclosed film strength test shows the real wear protection an oil provides.

 

[Tmoose]

He also posts from time to time on SpeedTalk. The folks there ( some with real motorsports experience ) say his film strength test rank some oils as inferior that have solved some difficult flat tappet cam and lifter, pushrod tip, and rocker arm problems that oils with higher 540rat ratings could not.

I believe there are kinds of loading and operating conditions that need qualities beyond "film strength." EP, anti-wear, viscosity index ( that might keep viscosity high even in very localized hot spots) come to mind.

 

[romke]

interesting reading...and quite a bit.

the problem with this kind of testing is that there is no explanation how the testing was exactly done and how the test carried out relate to actual operating conditions.

let's face it: engine lubrication is characterized through a few different lubrication regimes:

- pistons/cylinders/rings/journal bearings: usually full hydrodynamic separation of the moving surfaces apart from start and shutdown where occasionally contact between the mating surfaces will occur.

- parts where there is a form of point or line contact where elasto-hydrodynamic lubrication may be achieved within a certain speed and load range and where quite often also occasional contact between the mating surfaces is present.

it is only under the latter circumstances (and under startup/shutdown) that anti wear agents can be effective - as long as you have full hydrodynamic lubrication or elasto-hydrodynamic lubrication there is no contact between mating surfaces and thus anti wear agents have no influence on wear.

anti wear additives thus are only effective in contacts between camshaft, tappets/rockers/valves etc and eventual the gears that drive them.

for those parts, anti wear agents are a absolute necessity - and major oil specifications therefore very specific tests to ascertain that oils meet certain quality criteria. usually those tests are run in full scale engines - engines that are suitable for those tests because their valve actuation system is such that it can discriminate well between oils that do give the required protection and those who don't and produce results that correlate with actual practice in the field.

there have been several attempts to use simpler wear test like the Falex machine or the four ball test. time and time again it was shown that the results obtained that way clearly predicted the behavior of a engine oil in that particular test machine - and not in engines in actual service. the best ratings in those test machines where obtained by oils designed to be used in truck axles - but those oils are not at all suitable for use as engine oil.

anti wear agents for engine oils are based on complex compounds based on zinc and sulphur. since the way the compounds are structured, the amount of zinc itself has no direct relation to the protection that can be expected or the time the compound will be able to offer the protection needed.

anti-wear compounds are complex structures that not only play a major role in avoiding wear but they also have a major role as a anti-oxidant. in practice that means that wear protection in practice may strongly fluctuate with operating conditions. when such a multifunctional compound is used as a anti oxidant, it's original structure changes and subsequently such a changed molecule ("that gave it's life as a anti oxidant") can no longer give any wear protection....

today the amount of zinc and sulphur in the compounds in engine oils is reduced. the reason is that when they are emitted with exhaust gases, they may form a layer on the catalytic converter, reducing the effective surface available to reduce emissions. those new "lowSAPS" engine oils do contain less zinc, phosphor, zinc and other metallic elements, but yet offer protection as needed with modern engines.

simply classifying engine oils in a simple test may have all the advantages of being costeffective, fast and simple, but it does in no way justice to the far more complex
operating conditions in a engine in service.

 

[LionelHutz]

I believe he's using a version of the Falex machine. He's never posted his test method. He has posted that it is a quick test, I believe less than 90 seconds.

Overall, I would agree with your assessment that his tests show which oil would work the best to protect the wear part of his test machine. I believe it's mostly useless to predict which oil will perform the best in a particular engine.

I would also agree that the level of zinc in an oil does not directly correspond to the protection level provided. I do understand that the complete additive package determines the wear protection provided and it's not simply the zinc level which provides protection. But, for a flat tappet engine and especially for a flat tappet high performance engine, I would personally use an oil formulated for use in a flat tappet engine and it seems most of these do have higher levels of zinc. Are the higher levels required or is it marketing? I can't answer this but I would still trust the oil company to get it right more than someone who won't even publish their test method.

 

[drwebb]

FWIW- I have seen so-called EP/AW agents that facilitate wear in Falex testing. By preventing seizure, the blocks lathed the pin down about 2 mm in diameter under progressively extreme loads. Without that chemistry the blocks seized on the pin and the shear pin snapped at a relatively low load- although with no pin wear. So the agent provided better 'film strength', but under 'test' conditions having more relevance for cutting oils than engine lubrication . . .

 

[LionelHutz]

That brings up the question of which you want your oil to provide, continued operation with wear or siezing without wear.

I have seen the results on different web pages and in different advertisements. Typically there is a wear spot on the pin and the claim of better protection usually involves how much less wear there is.

 

[romke]

"wear testing" and "testing for suitability" may well be two different things, as the example that drwebb mentions shows. what you want from a engine lubricant is that it keeps your engine in such a condition that it can fulfill it's task, preferably for a long time. "wear" in itself is no problem, when the wear results in less then optimal operation it may become so.

a EP additive is a typical example: it will give more wear (in terms of loss of material) when used in a truck axle then would be possible with a lesser "agressive" additive. at the same time the wear is rather even, and thus the mating surfaces stay in working order with a smooth mating surface. when using another type of additive it would well be possible to reduce the wear to a much lesser figure, but because the load carrying properties would also be much worse, the gears would rapidly seize - so the actual life expectancy for the gear set would be uneconomically short.

in a valve actuating mechanism you want decent wear protection in terms of material loss, whereas the loads will be quite different from the loads on gears. thus, "agressive" additives would not be a advantage - the mechanism would develop quite a lot of wear, loosing it's hardened surface in a relatively short time - and thus in relatively short time the valve opening sequence parameters would be off....

a better score in a test thus not necessarily being better suited for the actual task in service.

when a machine is designed, the developer also chooses the amount of wear he/she sees fit - through the choice of materials, the shape of the components, the way they are manufactured, and also the type of lubricant to be used. those chosen parameters result in a technically and economically suitable life expectancy. that life expectancy usually has a fixed length (in hrs, miles, fuel used or whatever) - a little more would cost a lot more, less would not be economically acceptable. of course the design life of a bridge, a printing press, a car or a household mixer will differ - but all are the result of a careful process seeking the right balance between cost, live expectancy and economical acceptability.

even if it would be possible to increase the life span by the use of another type of lubricant, there remains the question who would actually want that. suppose you could double or treble the life expectancy of a car that way - what would mean you could drive it 2 or 3 times longer. some people might be willing to do that, most would swap the car for a newer model as soon as newer technological developments become available however.