Originally Posted By: fdcg27
I could just as well say that you have to prove your hypotesis.
But I don't need to, Doug already did, that was the point I made that you seem to have missed. Doug did millions of Km's coupled with thousands of UOA's AND random tear-downs to do actual physical inspection because he was doing lubricant testing for Mobil at the time with Delvac 1 5w-40.
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A properly maintained engine in typical light vehicle use will never be taken apart, nor will it need to be.
I agree. And a typical engine will never see a UOA either. And the use of them on this site is hardly in-line with their common use in commercial applications (which nicely corresponds with Doug's usage BTW).
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To state that the only valid measure of wear involves a teardown is a little silly.
Not sure how it being a fact makes it silly? Unless you are going to divine the wear measurements out of the engine you have no idea what wear has or has not occurred without tearing it down.
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Most of us are just looking for acceptable wear metals numbers.
Define acceptable? That's the issue here! We do UOA's, have no baseline for which to determine if they are acceptable or not and half the folks go off half-cocked over numbers they really don't understand in the context of the engine at hand. And again this jives handily with the article Doug wrote for this site which states that one must have literally thousands of UOA's for a given engine to properly be able to determine what "normal" is!
Ultimately GM doesn't give somebody a "normal" UOA spreadsheet for an LT1 and tell people to shoot for that as a target with whatever lubricant they see fit. They advise you run a GM-spec oil at the OLM interval to obtain optimal results. UOA's are used in commercial service to optimize lubricant operational life and monitor for things like coolant leaks, air intake tract leaks and signs of mechanical issues which are sometimes coupled with significant spikes in a particular metal or metals.
Similarly, Audi's testing yielded what THEY, the OEM, determined as acceptable wear performance using their requirements for an approved lubricant and what seems to be implied here is that through some UOA's and no actual measurements we've somehow managed to determine that some other lubricant is performing better than what Audi spec'd. While that may in fact actually be happening, a UOA is not proof of that, only a tear-down is.
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We aren't going to run an engine for thousnads of hours and then remove it from a vehicle ready for the yard so that we can tear it down and then break out the mics.
Yet that's exactly what people who have real data like Doug did. And that's exactly what the OEM's do. And they aren't doing UOA's and contrasting them to the tear-down measurements either. About the only situation I'm aware of where they are used is in F1, and these aren't your $20.00 specials. And the engines are still torn down eventually.
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The real message that I get from Doug is that when we're talking about PPM, even a 2X difference isn't really all that great.
But that's not what he states:
Originally Posted By: Doug Hillary
Secondly, it is easy to assume that by carrying out a UOA you will be able to determine how quickly the engine is wearing out. As well, if you change lubricant Brands you will be able to compare the wear metal uptake results and then make a balanced best lubricant choice to make your engine last longer.
Sadly that logic is seriously flawed.
Single pass (random) UOAs will provide some information regarding wear metals but unless you have a history of your engine’s performance up to around 1 million miles the results are simply that – UOA results! As an example a limit of 150ppm of Iron is a reality – after say 100k it means the lubricant should be changed and all is well. But what is the situation if you have 150ppm of Iron at 5k? Where would you look what would or could you do? So UOAs are really a diagnostic tool – one of many!
The other parts of the UOA Report will be much more valuable to you – it will tell you about the CONDITION of the lubricant and its suitability for further use. This will enable you to get the maximum safe use from the lubricant saving a valuable resource in the process.
So if it is normal for engine XYZ to generate 30-40ppm of Fe every 10K on an approved lubricant and you change to another lubricant that isn't approved and those numbers change that doesn't mean you can contrast those numbers to the earlier numbers. The new numbers are just the numbers for that lubricant in that application. To determine wear performance you still have to take the engine apart. No matter how inconvenient that might strike you as. Nobody said science was easy. It would be awesome to be able to just do UOA's until you got the lowest numbers and then choose that oil and proceed like a boss knowing full-well that your engine is wearing the least. But of course that's not how it works.
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If an engine shows 1 PPM of iron per K on oil A and 2 PPM of iron per K on oil B, will the difference in wear even be measurable with conventional measuring tools?
Probably not.
Is there a difference in wear?
Most certainly.
Does it matter at all?
Probably not.
You wouldn't even know where the iron was coming from with numbers that low. It could be rust, chelation, somebody could have eaten some iron pills and [censored] near the intake. Doug posted pictures (and measurements!) of various parts off an engine with 1.2 million Km's (that's roughly 750,000 miles) that had been randomly chosen as a tear-down candidate. This engine operated with an Fe condemnation limit of 150ppm IIRC and the oil was changed at around the 90,000km mark (55,000 miles). The parts still measured "as new" with that kind of mileage and that kind of lubricant "contamination" level/limit. The parts were returned to service! The liner looked immaculate BTW with visible cross-hatching still on the walls.
And regarding the difference in wear assuming more realistic examples: The UOA isn't necessarily telling us there is a difference in wear. Different additive packages will react to a surface and can result in a different measurement in a UOA. We don't know if these tiny particles in the 2-10 micron range are in fact the result of abrasive removal or chemical. They could even be the result of oxidation. A steel valve cover bolt operated in a Canadian winter accumulating a tiny amount of rust after a short winter run as the water gets to it. Then washed away by the oil the next actual warm up.
So I agree with your last statement: No, it probably doesn't matter. But the reason it doesn't matter is because we don't actually know exactly where the particles we see in the UOA are coming from. Ergo, we don't know what "wear" even is in this context. We know it is occurring, all over the engine (because an engine is always wearing while it operates), but we do not know how we are effecting it in each region that reflects the metal being measured (think of the potential sources of iron for example) and so we really don't know what we think we do with these simple numbers assuming they are in the range that is normal for that engine family. And if there IS an unusual spike, well that will likely warrant a manual inspection because you sure aren't swapping out a camshaft with another Blackstone kit.
The desire is of course to use a UOA as a substitute for an actual inspection. But anything unusual gleaned from the UOA will require an actual inspection. Just like there's no reason to tear down a properly operating engine there's really no reason to do a UOA on one either unless you suspect coolant ingress, intake tract contamination, a potential failure of some sort or are looking to optimize OCI length. The former reasons all potentially leading to a tear-down anyways.
The longest lasting gasoline engines get that way not because somebody optimized lubricant choice through UOA's and fretting over PPM, they got there due to good DNA and a lifestyle that is conducive to racking up excessive miles. So by that metric even if by some stroke of luck you actually reduced wear and were able to lengthen the life of your engine from 700,000 miles to 720,000 miles, in that context, as you said, does it matter at all? Given what sends most cars to the wreckers? probably not
BTW, this is a great discussion