High Silicon In Oil Analysis

[Daskuppler]

Hello Everyone,

 

I recently had an oil analysis done on my 14 forester.  Wear metals were high, but it was only the second oil change on the new block.  A total of 12k on it at the time of the oil draw.  Silicon was 49ppm.  Blackstone said check air filter.  I am running an AEM Dryflow.  These seem to filter equivalent to a paper filter and have good reviews.  Is this actually the case, or is the high silicon due to the aftermarket air filter?  I pulled the sample when it was warm and unfortunately right at the beginning of the stream.  Maybe the timing was the cause of high silicon?

The oil had about 11k on it with 1qt added.  The additive test came back with a little remaining and said I should not go beyond this for OCI.

[1 Lucky Texan]

new block? I'd say that's the source as they are sand cast. At least, I've read that before.

probably not worth changing anything but....?

[idosubaru]

Ensure all your leaks and filter is sealed with no air sneaking around?

If the intake is still stock, try another filter for just one oil change?

[Daskuppler]

9 hours ago, 1 Lucky Texan said:

new block? I'd say that's the source as they are sand cast. At least, I've read that before.

probably not worth changing anything but....?

Good to know!

40 minutes ago, idosubaru said:

Ensure all your leaks and filter is sealed with no air sneaking around?

If the intake is still stock, try another filter for just one oil change?

Intake is still stock so that's a possibility.  As far as I can tell, everything is sealed.

[Steptoe's photos]

Silicon eh? You remind me of a long time ago when I did an oil change on an old engine that then developed an oil light issue after a "good run" up the highway. I was wondering if the stuff I saw sitting at the bottom of the oil container 4 or 5 litre, white plastic, had anything to do with it.  I took the container to a government analytical lab to have it identified as "silica" which I was explained was basically , sand !! I took this back to the manager of the place I bought it - my boss, my work place ! He told me to have a look in another, and it was the same ! He directed me to pour the bottle into the bulk oil vat supplying the workshop. We did a few more - all the same !! An additive falling out of suspension ? Talking to head office in an effort to recover costs to resolve the oil pressure issue, I was basically told by them to have my legal reps contact theirs. I think after this point, the company stopped usig white plastic for their oil bottles.

[nvu]

I'd worry less about silica and more if there are flakes in the oil.  Silica can be remedied: better filter or shorter intervals between changes.

[GeneralDisorder]

 Important to note here that "Silicon" is different than "Silicone" (often found in engine sealants) and also different than "Silica" (which is often found in sand and dust) - these are all different materials with different properties.

Silicon is used in the BiMetal bearings Subaru uses for the connecting rod and main bearings:

https://www.aclus.com/bimetal-bearings-characteristics.html

Having seen the a few of these reman engines fail, and given the track record of this particular vehicle and the dealer doing the repairs - I would guess accelerated bearing wear is the reason for the high silicon. Might be minimal and clear up with more miles, or it might eventually throw a rod. We had one of those engines blow at about 13k miles. 

GD

Edited May 23, 2023 by GeneralDisorder

[Daskuppler]

10 hours ago, GeneralDisorder said:

 Important to note here that "Silicon" is different than "Silicone" (often found in engine sealants) and also different than "Silica" (which is often found in sand and dust) - these are all different materials with different properties.

Silicon is used in the BiMetal bearings Subaru uses for the connecting rod and main bearings:

https://www.aclus.com/bimetal-bearings-characteristics.html

Having seen the a few of these reman engines fail, and given the track record of this particular vehicle and the dealer doing the repairs - I would guess accelerated bearing wear is the reason for the high silicon. Might be minimal and clear up with more miles, or it might eventually throw a rod. We had one of those engines blow at about 13k miles. 

GD

Thanks for the input. I thought it was weird they told me to check filtration based on silicon when it should be silica if the air filter is bad,  it I don't really know how these things are reported.

For what it's worth, the last oil analysis on the original factory block that was burning oil reported 11 for silicon. Normal is apparently 30 and this analysis came in at 49. 

Could the high number still be break in since there's only a out 15k on the block? The oil was changed once after the first 800 miles.

Yes, this vehicle has a bad history. Fortunately the block has a 3 year warranty which will get it to 60-70k miles.

 

I attached the full report in case that helps with anything.

14 FORESTER-230429_230523_065854.pdf

[GeneralDisorder]

It could be break-in related. That said - in a perfectly machined, and perfectly cleanly assembled engine - assuming it is primed correctly, etc - there *should* be NO break-in except for rings - which would be cast iron, steel, and I think the top compression ring is plasma-moly (100% molybdenum) coated..... there's really nothing in an engine that *should* wear that contains silicon. The bearings should float on a film of engine oil and continued excess silicon in my opinion is an indication of sloppy clearance, assembly, or cleanliness. It may wear to a point and plateau there for a very long time - or it may just eat itself in short order. It's really hard to say - continue to do analysis and watch the trends. 

GD