UOA compare/contrast ... same sample source; analysis done two years apart

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FYI: How long can a used oil analysis sample sit on the shelf before you have to send it in for an analysis? How will shelf life effect the results?

You found an old sample you really wanted to examine but forgot. Is it still good?

I obtained an engine oil sample, divided it into two samples of equal size. I put them in identical lab supplied containers (plastic bottles). I sent one in immediately after the sampling and put the other on the shelf inside the air conditioned house. I then sent in the second sample for analysis, TWO years later. Here is the result:

Iron __________38_______41
Chromium _____1_______ Nickel _________ Aluminum ______9 ______9
lead __________ 1________1
Copper ________8_______8
Tin ____________5_______4
Silver ________ Titanium ______ Silicon ________ 6_______7
Boron ________ 9_______10
Sodium _______ 9_______10
Potassium _____ Molybdenum ____99______106
Phosphorus ____838_____923
Zinc _________ 963_____1035
Calcium ______2271_____2434
Barium _______ Magnesium ____17_______24
Antimony _____189______198
Vanadium _____ Fuel %Vol _____8.0______3.0
Vis CS 100C __ 8.3______ 8.9
SAE Grade ____20________20
Gly test ______Neg_______Neg
Abs Oxid______93_______100
Abs Nitr_______14________15

Same lab.

Ali
 
The tested oil was 0W30 (I think) in a Maybach 57s AMG with about 13,000 miles on the car and 5,300 miles on the oil. There is a lot of fuel in there from fast standing starts. Also, no sustained high load nor high speed driving to help get the oil temperature up there.

The test probably reveals that you are likely to get a reduced fuel contamination value. But not sure what actually happened to it. Note that clearly the oil was thinned into the mid 20 grade range, more so in the fresh sample.

One might learn from this. It takes a load of fuel, unobtainable in most of your engines, to get the viscosity to drop a grade. And really, one grade higher or lower should not make a discernible change in wear patterns. Mind you, this car was spec'd for a 40 grade oil, 0W40 Mobil 1.

Ali
 
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2 Yr Old Sample.jpg
 
That is great data. Thank you. So, the fuel is escaping slowly over time... volatiles!

And, with less fuel, I'd expect a little more 'metal' and 'additive' concentration, along with the visc/oxid/nitr increasing... the fuel doesn't dilute just the oil. It dilutes everything.
 
It's not clear which is the sample that was tested immediately and which is the one that sat for two years. Which sample had the higher fuel?
 
Thank you for this experiment and answering this question. I have the same dilemma with forgetting to send 2 old samples of oil to BlackStone for my CRV and Pilot over the past few months. I was concerned the results would be skewed a lot by the dirty oil or whatever is in there breaking down the plastic and leaching chemicals into the sample. I am still surprised there is a difference in phosphorus, zinc, and molybdenum though. Maybe variability in samples?
And, with less fuel, I'd expect a little more 'metal' and 'additive' concentration, along with the visc/oxid/nitr increasing... the fuel doesn't dilute just the oil. It dilutes everything.
So if I understand this right, without the fuel, the concentration of the sample, how ever much they use, is increased? But why not for the other elements? Does this have to do with how certain molecules are arranged and interspersed where as metals are free and unbound? If that makes any sense.
 
*&^ do I care. If you add anything without additives to anything with additives, the PPM drops. Our gasoline doesn't come with ZDDP, moly, calcium...... and, we are also at the mercy of the lab accuracy for anything not following a trend.

I have a few sample bottles sitting on the shelf and they also seem to evaporate some level, one was pretty drastic. I haven't ever seen my new oil quart gallon+ jugs lose oil an equivalent amount.
 
So billions of years in the ground and it didn't change in a sealed container after 2 years?
Good to know lol
 
Looks virtually the same on paper except the fuel differences. Interesting testing & Thanks for trying this.
 
FYI: How long can a used oil analysis sample sit on the shelf before you have to send it in for an analysis? How will shelf life effect the results?

You found an old sample you really wanted to examine but forgot. Is it still good?

I obtained an engine oil sample, divided it into two samples of equal size. I put them in identical lab supplied containers (plastic bottles). I sent one in immediately after the sampling and put the other on the shelf inside the air conditioned house. I then sent in the second sample for analysis, TWO years later. Here is the result:

Iron __________38_______41
Chromium _____1_______ Nickel _________ Aluminum ______9 ______9
lead __________ 1________1
Copper ________8_______8
Tin ____________5_______4
Silver ________ Titanium ______ Silicon ________ 6_______7
Boron ________ 9_______10
Sodium _______ 9_______10
Potassium _____ Molybdenum ____99______106
Phosphorus ____838_____923
Zinc _________ 963_____1035
Calcium ______2271_____2434
Barium _______ Magnesium ____17_______24
Antimony _____189______198
Vanadium _____ Fuel %Vol _____8.0______3.0
Vis CS 100C __ 8.3______ 8.9
SAE Grade ____20________20
Gly test ______Neg_______Neg
Abs Oxid______93_______100
Abs Nitr_______14________15

Same lab.

Ali

Shows how much variation there can be on an oil sample... wouldn't worry about 10% more or lesswear metals, it's just noise
 
I believe the fuel slowly evaps from the oil within the container, and is released when the bottle gets opened. This is why, again, in my opinion, that retests of the same sample, in all cases I have seen, show higher vis and lower fuel%.
 
I believe the fuel slowly evaps from the oil within the container, and is released when the bottle gets opened. This is why, again, in my opinion, that retests of the same sample, in all cases I have seen, show higher vis and lower fuel%.
I could accept that…at least on the fuel…based on a retest experience I had. I sampled 11/14/19, sent to both Dyson and OA (Amsoil). Fuel from Dyson: 5.2%, not sure of actual report date, but I think it was the fastest turnaround. Fuel was 2.6% from OA on 11/22. Asked OA to retest; came back 11/27 at 1.5%. I spoke to them, and they told me to “accept“ the 1.5%. I should have asked Dyson for a retest as well. I don’t remember my exact process, but recall pouring a little of the oil back and forth between the 2 bottles before sending off, to better assure they were equivalent.

obviously, this was not confidence-inspiring.

FYI OA’s KV100 did not change; and I had ordered the “Tuner” option from Dyson, which did not include visc, wear metals, or additives…just fuel, oxidation, nitration, sulfation, water, etc.
 
Volatiles will volatilize over time....unless you have a completely air-tight sealed vial with no headspace, the VOAs from the fuel end up in the air above the sample and when you open it to analyze, it's gone. When you sample groundwater for fuel (say a leaking underground storage tank a gas station) this is method and it's quite particular to get quality samples.
 
One of the things I learned from this test was the precision of the lab results. Every result showed a little bit of a more concentrated value with the loss of fuel in the sample. If there was no fuel dilution in the original sample the results would have been nearly exactly the same. Precision, a reason to use this lab for your testing. The only reason I stopped using them was for the superior analysis of the results performed by Dyson Analysis (that no longer exists as Terry retired).

Ali
 
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