Analysis of 4 UOAs and the engines they were taken

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I was looking around and found this document: http://www.nrel.gov/docs/fy06osti/38509.pdf

It was an analysis of a test of running trucks on biodiesel fuel. Now on pages 5-9, they have an analysis of engines from 4 Mack trucks that were part of the test, including results from UOAs from those 4 engines, on page 7. Unfortunately, the article didn’t include UOA results from the Ford engines. The 4 mack engines put on a combined total of some 750,000 miles before the teardown.

I’d like to verify that I understand their comments accurately. It appears to me that they are saying that the 4 Mack truck engines were roughly the same in terms of engine wear. The report says that “no significant differences were found” in some of the engine parts. Now on page 7, they produce UOA results (which are evidently from the 4 Mack engines). I see that iron levels vary from 13 ppm to 43 ppm.

Unfortunately, analyzing used oil analysis was not the purpose of the test. The test does not provide much information about the UOA results given. The second to the last paragraph on page 6 suggests that this UOA was done at the end of the test period, after the mileage was put on.

Looking at these numbers, can we conclude that differences in UOAs from 13 to 43 ppm of iron really are nothing to worry about? In other words, that results that vary that much, can still come from engines that show the same amount of wear?
 
Originally Posted By: paulri
The report says that “no significant differences were found” in some of the engine parts. Now on page 7, they produce UOA results (which are evidently from the 4 Mack engines). I see that iron levels vary from 13 ppm to 43 ppm..... Looking at these numbers, can we conclude that differences in UOAs from 13 to 43 ppm of iron really are nothing to worry about? In other words, that results that vary that much, can still come from engines that show the same amount of wear?


I'd doubt that its possible to draw any very firm conclusions. They appear to be using the phrase “no significant differences were found” loosely/subjectively, rather than statistically. With such a small sample size, relatively uncontrolled "experimental" conditions. (They used different oils, for example) and relatively subjective wear assessment, it would be hard to do anything else.

This does imply that these UOA analysis differences don't indicate gross differences in engine wear, but it doesn't mean that such analyses couldn't indicate any differences in wear, with a bigger sample.

I suppose that implies they aren't much use for monitoring non-catastrophic wear in an individual engine, but I THINK we already knew that, didn't we?
 
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4 engines with combined mileage of 750,000. Something less than 200,00 each. Not much for a HD diesel ... I think you'd have to go out to 500,000 each to see any real appreciable unique wear patterns developing.

I also think they were mostly concerned with upper cylinder wear as it regards bio-diesel ...

In that context, 43 PPM is not much and sice we don't know where it came from, I can't see it being to informative ...
 
Originally Posted By: BrocLuno
4 engines with combined mileage of 750,000. Something less than 200,00 each. Not much for a HD diesel ... I think you'd have to go out to 500,000 each to see any real appreciable unique wear patterns developing.



Unique, maybe, but from the description (bearing shells down to the copper, for example) isn't the wear already of borderline concern?

If so, taking it out to 500,000 might be expensive.
 
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