Originally Posted By: dlundblad
Yes I'm aware ppm means parts per million.. Regardless of how small that may be, it's still a unit of measure. I just find it odd 5w vs 10w made roughly a 50% difference in iron wear. Both oils were pennzoil conventional. It's not like it was valvoline conventional vs say mobil conventional oils. See what I'm saying?
No I don't because you are ascribing more value to that variation in the PPM values than is actually present. The articles on the front page by Doug Hillary and Dave Newton spell it out quite well in terms of the amount of trending necessary to draw any sort of useful information about the wear signatures for a given engine on a particular lubricant. And that still doesn't give you REAL wear, which can only be measured through tear-down testing.
Food for thought:
Doug Hillary ran a series of OTR trucks (500HP Detroit Diesel engine) when he was doing fleet oil testing for one of the majors. He did periodic tear-down inspections on the rigs where one of the engines would have a random cylinder pulled and inspected.
His condemnation point for iron wear was 150ppm. Other contamination that was tracked was soot loading, oxidation....etc. Average iron measured at OCI was something like 105ppm IIRC.
He was kind enough to post a picture of a liner and the bearings from one of the random pulls on here. The engine had 1.2 million Km's on it and the liner looked like new with the cross-hatching still visible in the bore. The bearings were measured and were still within "as new" spec and so everything was put back together and the truck returned to service. IIRC, he recently noted it was still in service and has something like 2.5 million Km's on it now.
Many on here would have a cardiac episode even thinking about 150ppm of iron in a UOA.
In contrast, a past member BuickGN had a UOA done on his 650HP Grand National and it showed perfectly acceptable levels of wear metals. However it was making noise and so he tore into it and the bearings were completely gone out of it. Yet there was no sign of that in the UOA.
An extreme example for sure, but it does go to show that what one THINKS they are gleaning from a UOA isn't necessarily what is actually taking place. There's no $25.00 test that's going to give you the data you get from a tear-down. The primary purpose of a UOA is to track contamination levels in the lubricant and lubricant health. They can show you coolant leaks, intake tract leaks....etc. But the metals measured are not supposed to be a barometer for gauging actual engine wear. Sure, a 100ppm spike in lead may indicate a potential bearing issue, but as noted by Blackstone, it may also just be a particle streak. This is also why UOA's must be trended.
I placed the emphasis on MILLION not because I didn't think you knew what that meant but simply because when you are talking about a measure of 5 or 10 in relation to something measured in a scale of a million, one must be conscious of that when considering the gravity of that reading.
