Patman
Staff member
More and more, I truly believe each lab is going to give a totally different set of results even with the same oil. I have yet to see an oil sample that has been sent to two different labs, come back looking even close.
Valvoline 10W-30 SL- All Climate
- Thread starter Greg Bohn
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In an attempt to determine which lab, if any, has the most accurate numbers I now have six sets of results to compare and contrast. I just got back two more results from Oil Analyzers.
I have results from three labs on samples from the same 1 Qt. bottle of unused Valvoline 10w30.
I also have the results from three labs which I sent 'the same' used oil from one of my cars. I actually drew enough oil for three samples when I sampled the engine. I sent two samples out at that time (to Herguth and Blackstone) at kept the third sample in a bottle. After about two weeks I sent out the third sample to Oil Analayzers.
As I mentioned in a prior post, the 'used oil' is from my cars last change at Valvoline Instant oil change. It's supposed to be close to what they sell in the retail bottles (at least according to the guy at VIOC).
The results are:
I was hoping to compare at least the three labs 'used results' against each other, as well as the three 'unused' results against each other to determine which labs if any matched.
Since it looks like none of them match that closely (at least for Ca, Zn, and P), I guess I'll have to think about what conclusions can be drawn from the results.
I know I really should have sent out all results at the same time, but when I started this I didn't think I was really going to end up needing to get results from three labs...
Yep, I've been specifying oil Brand/type/weight.
In another thread (under Used Oil here) I have results from used samples of oil which should be similar to this unused oil. These are also results from the same two labs.
It looks to me as thought tests for the 'high concentration' parts only resemble each other when getting results from the same lab (for similar or the same oil).
The 'low' PPM wear metals generally seem to match more closely between different labs than the 'high concentration' additive measurements.
Herguth told me their metals results should be accurate within 'a few PPM'. I've seen another thread where someone claimed OAI says their results were supposed to be within '+/- 2 PPM'.
I wonder if the real accuracy might be more like 'plus or minus x percent +/- a few PPM'.
If that's the case, and 'x' is something like, say 30%, very low value results would be largely driven by the +/- 2 or so PPM part. But higher concentration values would become mainly influenced by the 'x %' part.
Even that doesn't seem to account for the results I got earlier in this thread (from three labs) which has OAI saying a virgin oil had 38 PPM Boron, with the other labs reporting 4 and 5 PPM.
Guys and Gals I feel your pain on the repeatablility of a lower cost oil analysis sample.
One of the reasons I began offering a "consumer Kit" was due to the variability of each lab. We offer my eye and judgement as a last QA/QC of whatever results I'm digging into. My own contracted lab makes mistakes and I usually catch them before you the customer see them.
Knowing the customer/equipement in a personal way via email and exchanging info really helps but most labs will not be able to make money and tie up their techs on the phone or computer that way.
The key is to standardize your variables and keep samples you are comparing on as equal footing as you can. Use the same lab,same oil,same engine,same ambient temps,etc.
Using the relative differences from the same lab is not acceptable for alot of the perfectionists out here but it is still reliable in a low cost test to procure data to make decisions on oil and engines.
One of the reasons I began offering a "consumer Kit" was due to the variability of each lab. We offer my eye and judgement as a last QA/QC of whatever results I'm digging into. My own contracted lab makes mistakes and I usually catch them before you the customer see them.
Knowing the customer/equipement in a personal way via email and exchanging info really helps but most labs will not be able to make money and tie up their techs on the phone or computer that way.
The key is to standardize your variables and keep samples you are comparing on as equal footing as you can. Use the same lab,same oil,same engine,same ambient temps,etc.
Using the relative differences from the same lab is not acceptable for alot of the perfectionists out here but it is still reliable in a low cost test to procure data to make decisions on oil and engines.
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