UOA analysis after switching oils

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Oct 8, 2024
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Hey everyone,

I’ve got a question about oil sampling and analysis. I usually run 0W20 Pennzoil Ultra Platinum during the winter, but in the summer, I switch to 0W40 Mobil 1 FS for autocross. I was thinking of pulling a UOA (used oil analysis) after running the 0W40, but I recently heard something that made me second-guess the timing.

I was watching The Motor Oil Geek on YouTube, and he mentioned that if you switch oil formulations, you should ideally run the new formulation (in this case, 0W40 Mobil 1 FS) twice before pulling a sample. This is because residual oil from the previous formulation (my 0W20 Pennzoil Ultra Platinum) could skew the results on the first run.

Does anyone have experience with this? Is it better to wait until I’ve run the same oil twice before doing a UOA, or would it still be fine to pull a sample after the first run of 0W40? Any insight would be appreciated!

To clarify can I sample the 0W40 after the 0W20. Or should I only sample the 0W40 on my second oil change (after having run the 0W40)? To avoid cross contamination in my UOA. Video starts at 1:00.

Thanks!
 
It aint going to happen. You will never drain the residual oil out unless you disassemble the engine.

What exactly are your UOA goals? You will be better off asking questions here vs his videos.
 
This would depend upon what you expect to gain from the UOAs in terms of knowledge and data.

The foremost thing to understand is that small sample sets (especially of only 1 or 2) are, in no way whatsoever, a means of understanding how well one product compares/contrasts to another. So if you're trying to decipher the wear traits, one lube relative to another, you're on a fool's errand. UOAs are most certainly able to discern how lubes perform in terms of wear control, but only when used in a true statistical analysis manner (establishing base data, then trial data, meaning 60 samples at a bare minimum to understand avgs, means, stdevs, etc).

Singular UOAs are good for understanding general contamination loading, basic lube characteristics, etc.

Start your understanding of normalcy and how it applies to UOAs here:
 
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It will skew the viscosity reading. I have two uoa’s showing lower than anticipated viscosities after switching from 0w20 to 5w30 and from 0w16 or 0w20 (unsure what was previously used) to 5w30. As stated above, there is always some residual oil left behind. So, in terms of wanting to assess a particular oils viscosity (aside from shearing/fuel dilution) yes I would wait until the second oci with the same oil.
 
No one will ever determine comparative oil quality or wear results using a spectrographic analysis like this is being done. Comparative wear analysis between oils is complicated and expensive, mostly to isolate the singular variable of the oil.

It's nice he's including other analytical processes but it still isn't what's required.
 
No one will ever determine comparative oil quality or wear results using a spectrographic analysis like this is being done. Comparative wear analysis between oils is complicated and expensive, mostly to isolate the singular variable of the oil.
BOOOOOOOOOOOOOOOOOOOOOOM!!!

People here try all the time. Not going to happen. All it shows are folks who really don't understand lubrication.
 
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