Additives settling out of oil. Test results...

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Sep 3, 2021
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I've seen many comments over the years about the additives or other components of oil settling out of it and that you should shake the bottle to mix them back in. Maybe it's true, maybe it's not... so I thought I'd test the theory.
Based on testing of a bottle of oil that sat on the shelf for about 5 years and was not shaken (only very gently moved) to do these tests the answer is...

Nothing settles out that matters. Full details posted in this video I did to document how I tested it.

 
Excellent test and video! (y)

One of the most famous myths your video disproved was everyone thinking the gray stuff on the bottom of oil containers was moly that had fallen out. Your video shows that's not the case. I wonder if the gray stuff is just dirt or something that doesn't get "cleaned" out during the refining process?
 
The bottom sample did show about 10% more Mo and 2.5x more Si.
To me, it does show additives settling a little, but not nearly enough to worry about.
 
The bottom sample did show about 10% more Mo and 2.5x more Si.
To me, it does show additives settling a little, but not nearly enough to worry about.
But for one or two of the others the trend of the three (top middle and bottom) was not as you would expect. But I agree with you overall, it might be showing a very very weak effect but so little it's not worth the worry. I would love to get that gray stuff off the bottom and send it to a lab that could pin down exactly what it is.
 
I'm not convinced by the video. It's a sample of one. There was a thread on the subject a while back. I offer it as another perspective.

 
I'm not convinced by the video. It's a sample of one. There was a thread on the subject a while back. I offer it as another perspective.

Yes, it's just one test. Other brands might show some differences.

I think everyone agrees there is some sort of grey stuff people find, as I did, on the bottom of bottles of oil. As the test results show, it is not any of the normal additives settling out because the tests show all the additives are still in the oil and in nearly identical amounts from top to bottom. If the gray stuff was one of the normal additives that gets tested for and ALL of it had settled then obviously none of it would have been left in the top sample. And since I stirred up the gray stuff so it was mixed into the bottom sample, the bottom sample would have been very very high in whatever additive or contaminant the gray stuff was. Yet that was not the result. So we know that when you mix it into only the small remaining bottom oil that whatever it is does not show up as one of the things (good or bad) normally tested for. Whatever it is, it's not one of the things normally tested for, good or bad.

What I think we can say with reasonable certainty for this oil is this...

- the additives considered important to regular motor oil and which are tested for as part of a routine oil analysis did not settle out.
- we know that the gray stuff is not one of the contaminants *which are tested for as part of a routine oil analysis* because it did not show up in the bottom sample which would have had all of it mixed in for the sample tested. So it's not dirt (silicon) which had all fallen to the bottom. It's not iron, it's not aluminum, etc. .

In a quart there are about 15,000 drops of oil. A drop in a quart is the equivalent of about 66 ppm (parts per million). If you saw the gray dust in the video and imagine you could manage to scoop it all up I doubt all of it together would even be the volume of a single drop of oil. But if there was a full drops worth of gray dust that means the amount of it in a quart of oil is no more than 66 ppm. That small amount is unlikely to be a problem.

We can make an estimate of the size of the gray particles. Based on info here (https://www.machinerylubrication.com/Read/781/particle-contamination) particles large enough to be damaging (20 microns) would have settled to the bottom in less than an hour in ISO22 turbine oil. That's similar to 0 weight motor oil. Even if it took 10 times as long to settle out of common weight motor oil it would still take less than a day. Assuming this gray stuff took months or years to settle out that would mean it is surely under 10 or less microns, very fine material indeed.

My conclusion about the gray stuff in this particular brand/bottle is that there is nothing to worry about because the expected particle size and quantity are both so small. But if someone is worried that the gray stuff is bad the best thing to do with oil that has been sitting is DON'T SHAKE the bottle. The good stuff hasn't settled out and the potentially bad stuff, the gray stuff, is stuck to the bottom. Don't shake it and the gray stuff will stay stuck to the bottom of the bottle and the good stuff will be in the engine.

On the other hand if you think whatever it is is good stuff that has settled out go ahead and shake the bottle.

In either case you'll only be excluding or mixing back in about 66 ppm of something so probably safe either way.
 
i always drain around 3/4 of the jug of oil then put the cap back on and act a 14 year old at night just in case since there have been cases of it falling out of suspension. myth or not the practice doesn't hurt and i see i wasn't a total fool :)
 
i always drain around 3/4 of the jug of oil then put the cap back on and act a 14 year old at night just in case since there have been cases of it falling out of suspension. myth or not the practice doesn't hurt and i see i wasn't a total fool :)
I do the same except after a 1/4 or so poured.
 
So you know the sediment is “dirt” or some other form of contamination?
I never said it was dirt just like you said "If there is dirt in those bottles that’s really a problem." So I am saying GTL is supposed to be cleaner than crude.
So what do you think it is?
 
I never said it was dirt just like you said "If there is dirt in those bottles that’s really a problem." So I am saying GTL is supposed to be cleaner than crude.
So what do you think it is?
Well I think it is additive fallout, that's pretty much what Pennzoil said when they commented on it. Sure GTL is "cleaner" but that doesn't have anything to do with precipitate formation or physical "dirt" in the base stock, it means there are fewer sulfur compounds and unsaturates in the intermediary. It's still hydrocracked like any other Group III base. It's far cleaner in that respect since it's synthesized from methane. Crude oil is "dirty" in that it contains a plethora of undesirables but the formulators do a pretty good job of removing those.

Which is a way of saying I don't know either. But I bet Sopus does, I'm just not betting on a $30 spectrographic analysis to be the definitive answer.
 
We can make an estimate of the size of the gray particles. Based on info here (https://www.machinerylubrication.com/Read/781/particle-contamination) particles large enough to be damaging (20 microns) would have settled to the bottom in less than an hour in ISO22 turbine oil. That's similar to 0 weight motor oil. Even if it took 10 times as long to settle out of common weight motor oil it would still take less than a day. Assuming this gray stuff took months or years to settle out that would mean it is surely under 10 or less microns, very fine material indeed.

If it's smaller than 20 µm then likely most of it will pass the oil filter. I don't think that's a good thing or it doesn't even matter.


My conclusion about the gray stuff in this particular brand/bottle is that there is nothing to worry about because the expected particle size and quantity are both so small. But if someone is worried that the gray stuff is bad the best thing to do with oil that has been sitting is DON'T SHAKE the bottle. The good stuff hasn't settled out and the potentially bad stuff, the gray stuff, is stuck to the bottom. Don't shake it and the gray stuff will stay stuck to the bottom of the bottle and the good stuff will be in the engine.

My first thought when watching your video. I used to shake any bottle before, but I will have to rethink this common practice. That said I have never observed anything settling out yet. Perhaps your old Shell example is a rare exception? Even then the result of your OAs remain true anyway. Common additives do not settle out. Thank you very much for your effort.
.
 
So if this is correct then what is settling out would likely not appear on a spectrographic analysis:

 
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