I disagree with the thinking that there is no difference between 5ppm and 20ppm in a UOA! I know that there is not that much of a margin of error on the UOAs. If that were the case, then someone who does UOAs on every single oil change would notice major swings in their reports. But this is not the case, most people find that if they keep using the same oil, their UOAs definitely do not vary by anywhere near that much, they are relatively close each time so long as the climate and driving habits don't drastically change.
I could see it varying by 10 or even 20%, but certainly not 400%. Sorry, it's just not going to happen. We've even proven it on here with a few people sending the same oil to a couple of different labs. Not one of them showed anywhere near that much of an error.
So, if you see a trend with your vehicle showing one or more of the wear metals being higher than you like, such as was the case with my LT1 Firebird showing higher lead, then you make a switch and see if it works. In my case it did. And I'll bet the farm that my future UOAs also show my lead remaining low as well, that it wasn't just a fluke.
I'm sure Terry Dyson will chime in here as well, and prove that UOAs are indeed valuable and the varience in the reports isn't anywhere near what Russ says it is.
I agree that if you're seeing a bunch of 2s, 3s and 4s on your UOAs, don't worry about trying to get those down to 0s and 1s. But if you're seeing consistent double digits in a 3k report, you could certainly try to get it into the 5ppm or less range if you can. And many people on here have been successful in doing just that, simply by switching oils or trying out different things.
[ January 12, 2004, 01:20 PM: Message edited by: Patman ]