UOA Wear Metals Cause Engine Wear?

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Dec 6, 2003
Austin, TX
OK...here's a question for the "real" experts. As long as an oil's insolubles aren't excessive, TBN value still acceptable, and there's no glycol, fuel, water in it, i.e., the add pack isn't terribly depleted, what harm is being done to the engine if the wear metal values are on the high side? If I understand correctly, the wear metals being measured in a UOA are less than a micron in size and are essentially in solution and are in the parts per million type quatities. I understand that high values indicate problems for an engine already broken in. But will high values cause problems in and by itself over the short run?
I'm definitely not an expert like Molakule or Terry Dyson but I'm sure both of them would say that when you have high wear metals in the oil, this tends to have a domino effect, causing more wear as a result. In other words if you've got 50ppm of iron and 50ppm of lead in there, it'll just multiply all of the wear metals that much quicker, as the oil then becomes somewhat abrasive.
Thanks for chiming in Patman. If I understand what your saying, it's kinda' like a sand blasting effect. No?
It depends on the metal and it depends on the particle size.

For example, I don't think atomic Pb or Cu in solution will accelerate metal wear. However, break off some Si, Cr or Fe in chunks and as Patman sez, domino effect....now the interesting thing is that these chunks in of themselves may NOT be detected in an atomic UOA, whereas their effect is unmistakable in a UOA report.
Pablo, if I understand correctly, what you're saying is that you won't see high wear metals in a UOA (sub micron stuff) if there isn't "large chunks" (1-100 micron stuff) in the oil too?
427ZO6 -


you won't see high wear metals in a UOA (sub micron stuff) if there isn't "large chunks" (1-100 micron stuff) in the oil too?

Not exactly or not always, I suppose some of this is wrapped in the semantics - but I'm thinking submicron metals would have have to be pretty high to cause more wear JUST from their presence.....but in practical terms that would be the least of your worries! (ie get after the root cause of the wear!)
Pablo, OK. I think we're on the same wavelength. Thanks for taking the time to respond. I'll go back to my corner and think some more.
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