Yeah sorry I no longer have access to all the ASTM tests. But even if they do use spectrographic data here it is a controlled test, unlike UOA from street vehicles. Street engines have a host of sources for wear. But if all you wanted to know was “wear” then maybe you’d get something.True, it does make a direct measurement of the cam lobe. Depending on the API rating/license certification as time went on, the max wear limits have changed. Seems to have went down from around 120 um to 60 um (micrometer) from what I can find. Also the ASTM D6891 is ran for only 100 hours, and it's done on the fired engine at very low RPM (800 & 1500 RPM) where the wear rate would probably be pretty low compared to much higher RPM.
The ASTM D6891 does reference also making an "iron wear metal concentration" measurement ... so UOA. But doubt it's used as part of the criteria to pass or fail as the direct measurement is the primary factor. Wouldn't know how the UOA comes into play without seeing the entire ASTM spec, which I'm not going to pay to see, lol. In a test like this where the engine run time is pretty low time and low RPM in the scheme of things, obviously a direct wear measurement is the best way to do it.
I'm wondering if any controlled tests have been done that do a much more long term engine wear test (like 100K+) on their chassis dyno (like Mobil, BMW, etc do) and they take regimented UOAs along the way as monitoring data/info before the test ends and they do a final tear down, inspection and measurements. Seems like controlled UOAs would be beneficial information in a very long term test like that.
ASTM D6891-21e1
Standard Test Method for Evaluation of Automotive Engine Oils in the Sequence IVA Spark-Ignition Enginewww.techstreet.com
"The primary result is camshaft lobe wear (measured at seven locations around each of the twelve lobes). Secondary results include cam lobe nose wear and measurement of iron wear metal concentration in the used engine oil."
Thanks for the discussion here.