UOA question

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Nov 29, 2002
If you switch viscosities but stick with the same brand of oil will this skew results? Thanks,,,op
I believe that exact results are skewed if you don't use the same batch of oil for multiple UOAs to find trends, sucesses and pitfalls. There's plenty of variation even in a given brand and formula amongst production runs.
So if I were to use M1 EP for a run then decide to switch back to regular M1 synthetic, then do a UOA, the results won't be accurate disregarding production quality, etc... am I right? I think I'll just stick with M1 synthetic,,,,op

You have to consider carefully what a UOA can tell you:

- Oil condition through FTIR (oxidation, nitration) - this will be compromised by possible differences in the base oil mix.

- Wear metals - the concentration will be what it's going to be, regardless of the oil composition

- Condition of the add pack - switching oils always messes this up. Different formulations have different adds.

So, the bottom line is that you lose information about the condition of the oil itself, and of the add pack. Wear metals will be representative, but have limited value for assessing the condition of the oil.

Any oil change will change the results, although if in brand you stayed with the same formulation (that means knowing what is going on behind the scenes with the batches), and IFF you could garantee the same usage, driving, weather, fuel, dust, etc., you might see a different wear trend with a different viscosity.
As a general rule, I see wear go up in an engine that should run 15W-40 when the viscosity drops, and a trend upwards when it goes too high. Although the upward is more difficult to pinpoint as the causes of thickening (soot, dirt, oxidation) can be causing the wear, rather than just the viscosity.
The bottom line is that if you switch hit (swapping oils and doing UOA) you've added unknown variables to what you're looking at. Someone real smart, like Terry, can probably read beyond the noise, but most of us who can only see the most obvious indicators tend to just confuse ourselves.
Like I mentioned before, I want to try a 5w40. T&SUV (IF I CAN FIND IT!!!!!!!!
) It's still a Mobil product but seeing it's a thicker viscosity at operating temp. I was curious to see if something like a thicker viscosity would skew things up.

Seems like there's alot more to it to really get a straight answer. Thanks guys,,,,op
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