Silicon in UOAs

[Danh]

I'm puzzled by the air filtration conclusions used oil analysis providers make based on silicon content of oil samples. I guess it makes sense that dirt being inhaled by the engine includes silicon, but does a low reading really mean filtration is good and a high reading means it is bad?

If there was no air filter at all, dirt and silicon would be inhaled, a portion would work its way past the rings and wind up in the sump (doing damage on the way). However, if oil filters are at least as effective as air filters, wouldn't the silicon then be eliminated by the oil filter? So, if the last several miles before the used oil analysis sample was drawn were in clean air, wouldn't silicon levels look OK?

Perhaps I am wrong on this, but it seems to me that silicon in oil samples are either from paticles so small they wouldn't have been captured by an air filter anyway, or are particles that simply haven't passed through the oil filter yet. In other words, aren't silicon levels really more a function of the air quality the engine operates in rather than the quality of the air filtration system?

Thanks for any insights you may have.

 

[tinmanSC]

This is actually a fancy bit of logic. And... I'm not really sure how to answer it. I'd love to see the explanation!

 

[Barkleymut]

Good observation. I am curious to see the responses by some of the experts on here. Perhaps while the silicon is passing thru the cylinder it gets ground down into small enough bits that an oil filter would not collect it and then ends up in the sump????

 

[JHZR2]

I've never been one to accept filtration as the Si source automatically.

 

[SERonBLAST]

In new and lower mileage vehicles the silicon particles are usually from the break in on engines, most seals and gaskets are silicon based. I have never heard of this being from poor air filtration so iam not sure about your situation. And i am no expert.

 

[LargeCarManX2]

Something more to consider regarding silicone readings. It would make more since to flag insoluble levels along with silicone levels together in a used oil analysis.

Silicone levels without high insoluble levels could be the oil or other factors alone.

This statement would make a better argument regarding air filter, pvc leakage, or dirt ingress to the engine leakage for silicone levels.

It appears that most new oils show high levels of silicone. Also, in areas close to oceans, just the levels of silicone would be higher! I believe the answer is insoluble levels in used oil analysis combined with silicone levels.

 

[mechtech2]

Silicone and silicon are different words, with different descriptions.

The oil filter can let small particles past it.
They would have to be small to get past the rings into the oil in the first place.
Also, Silicon [sand] particles may be present in the fist few OCIs because of sand cast engine parts that are not perfectly clean to begin with.

 

[Slippery_Pete]

Way to come in on a bang

Someone should do an experiment with a paper filter vs. a high flow filter like a K&N.

 

[OneEyeJack]

I would be more concerned about any trend in such data that the absolute level. If you are collecting silicon in increasing numbers or even numbers that stay level you might look around for a problem. One hit early on may not mean much, if it goes away. Twice in the past we found contamination in the new oil, from the drum it was contained in and that has also been a problem at dealerships and repair shops that drum their oil to save on expenses, especially if they dispense it into empty containers or use a lube gun.

 

[mechtech2]

Originally Posted By: Slippery_Pete
Way to come in on a bang

Someone should do an experiment with a paper filter vs. a high flow filter like a K&N.


Check out the air filter section in this forum.
Been done.
And done again.

 

[mechanicx]

I think air filters are much finer filtration than full-flow oil filters. A fluid filter with as fine filtration would be too restrictive. Filter council If you look at table 2 in the link dust can often be under 10 microns and be as small as .1 micron. Most oil filters capture very little under about 10 to 5 microns or so.

 

[NateDN10]

Feel free to correct me if I'm wrong, but aren't all the elements that are detected by oil analysis *dissolved* in the oil? No oil filter can filter individual atoms dissolved in the oil. Only insolubles can be filtered.

 

[mechtech2]

Originally Posted By: NateDN10
Feel free to correct me if I'm wrong, but aren't all the elements that are detected by oil analysis *dissolved* in the oil? No oil filter can filter individual atoms dissolved in the oil. Only insolubles can be filtered.


You are on the right track, thinking wise. Oil filters are from OK to pretty good about particle size. And what is filtered out is NOT going to be in a used oil analysis!

Therefore the used oil analysis tells us what?
Therefore I don't do used oil analysis.

 

[mechanicx]

As the filter council link explains air filters are finer filtration and some dust or silicon is too small to be trapped by the oil filter but can be trapped by the air filter.

As far as silicon in an UOA while the size of the silicon is not measured it is an insoluble and not just dissolved to atomic level, and it is probably assumed that first the air filter should capture it in its smallest normally occuring form (so the level should be low) and if the level is high the silicon includes particles too small to be caught by the oil filter but large enough to cause engine wear, ~5-15 microns. Besides, silicon level is only one factor that an UOA detects.