BITOG - Why iron ppm numbers are not good wear indicators.
And good info regarding uoa's in general.
Quote:
...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.
|
http://bobistheoilguy.com/used-oil-analysis/
Quote:
Originally Posted by BaBaFlyingSheep
I assume that at some point down the line (maybe 250k+ miles?), there's been so much metal removed from the engine, that the oil just can't protect the gaps between moving parts (cylinder walls), and the iron wear will increase drastically.
|
I don't think this is the case. I've never heard of wear becoming so bad that the oil cannot protect the gaps between moving parts. I recall a trend of uoa's on nasioc several years ago on a high mileage WRX. Lead jumped up quite a bit and it was speculated that a bearing was going out. OTOH, I've seen uoa's on cars with 250,000 miles and uoa wear was lower than similar cars with only 50,000 miles.