Originally Posted By: Jorge
UOA is for determining the proper OCI, oil contaminates and if a mechanical issue exists in the engine. A UOA can not tell you if one oil lubricates better in your engine than another. You need to run the oil test sequence like the A3/B4 or car mfg.'s oil test sequence to determine the oils actual lubricating properties.
What a UOA can and can not tell you
Being rather dumb or perhaps still ignorant about correct interpretation of UOAs, I'm still puzzled by this explanation (I read Doug's write-up, and I'll admit it doesn't make a lot of sense to me).
I'm almost certainly missing something here, so I'd appreciate it if Doug or some knowledgeable person could help me understand this.
My thinking is that a series of, say 4 UOAs of a specific oil in a specific engine over distance, let's say a UOA done every 2500 miles until 10K mile....may indicate that the oil is all used-up at between 7500 miles and 10000 miles, because the FE or aluminum levels started climbing rapidly, and perhaps low TBN, etc, etc.
Another, different oil, when run the same series of UAOs on the same motor under the same general conditions, may indicate no sudden climb in metals between 7500 miles and 10000 miles and may still have sufficient additive and low TAN, etc, etc.
Why would/could one not then deduce that oil B may be a better oil than oil A for that engine, under those conditions?
In my view, if the series of UOAs for each oil indicates a progressive decline over the distance, and provided the UOA results are not out of bounds between consecutive UOA test of that same oil, once could assume the UAO results are valid...and the natural conclusion reached.
Is this assumption totally invalid? If so...why? I have a TINY grasp of probabilities and margin for error, etc...but repeatable results always makes me feel that the test should be reasonably valid.
Thoughts?
