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High Silicon in Oil Analysis Solved (I think)

snopercod

Well Known Member
Ever since my first flight in 2014, my oil analysis has come back "high silicon". The standard response has been "Your air filter sucks". It's a K&N, which is known to let more "stuff" through than some others, but I just didn't believe the filter was at fault because I don't fly off of dirt strips or in sand storms. So I ran an experiment. I had originally vented my crankcase with silicon rubber coolant hoses which ran to an oil separator, the drain of which was plumbed back to the crankcase with more silicon rubber hose. At the last annual back in August, I re-plumbed the system so the separator drain went to a little catch bottle rather than back into the crankcase. Wonder of wonders, the latest silicon reading went down from the 30-35 range to 14 this time. I'm calling "problem solved".
 
My experience

I also have an air oil separator that returns the oil to the crankcase. I just received my first (56 hours total time) oil analysis report and my silicon reading is 10. I used the silicon hoses provided by Antisplat. Maybe my hoses different than yours? Mine are the blue ones.
 
Go ahead. Make a liar out of me :D My hoses are green on the outside and red on the inside. They are coolant hoses for 18 wheel trucks. Maybe the anti-splat hoses are lined?
 
Sorry

Didn?t mean to. 🙁 I?ll check the inside color tomorrow. And I also have a K&N filter. Mine is Horizontal induction.
 
K & N Filter

I use a K & N conical filter on my Rocket. I don't even bother "treating" it with their magic oil anymore - I looked up my last 10 oil sample analysis' and had an average of 6 ppm for silicon.

David
 
Ever since my first flight in 2014, my oil analysis has come back "high silicon". The standard response has been "Your air filter sucks". It's a K&N, which is known to let more "stuff" through than some others, but I just didn't believe the filter was at fault because I don't fly off of dirt strips or in sand storms. So I ran an experiment. I had originally vented my crankcase with silicon rubber coolant hoses which ran to an oil separator, the drain of which was plumbed back to the crankcase with more silicon rubber hose. At the last annual back in August, I re-plumbed the system so the separator drain went to a little catch bottle rather than back into the crankcase. Wonder of wonders, the latest silicon reading went down from the 30-35 range to 14 this time. I'm calling "problem solved".

I don't believe that a high silicone content in your oil is a "problem" per se. It is reported as it helps to identify other "problems" such as poor air filtration.
 
Do you have an oil filter? If you do and you happen to use Dow DC-4 Silicone lube on the filter gasket, that can raise the si level in the analysis.
It does in my reports if I get "sloppy" with the lube.
Mel B.
 
Do you have an oil filter? If you do and you happen to use Dow DC-4 Silicone lube on the filter gasket...
Yes on the oil filter and I did always use DC-4 on the gasket. This last oil change, though, I installed a Tempest EZ-spin so in 25 hrs. we'll see if that makes a difference. I also have the RTV rocker cover gaskets.
 
Go ahead. Make a liar out of me :D My hoses are green on the outside and red on the inside. They are coolant hoses for 18 wheel trucks. Maybe the anti-splat hoses are lined?

Since you have all under control now, you can always put the hoses back on to show the silicon goes back up. It's bad when silicone gaskets, hoses, sealants etc push up the numbers, as it is the best indicator of air filter effectiveness, and thus barrel wear. Particle size and count measurements also can help augment the oil materials measurements for engine health understanding.
 
Normal Silicon

I got my second oil analysis back after switching to a catch bottle rather than draining the oil separator back to the crankcase. Silicon was still normal for twice in a row. This reading was 17, up from 14 last time and in the twenties previously and forties originally. So the long term trend has been down. Hmmmm...
 
I think we need to distinguish between the element silicon and the elastomer silicone.

From Wikipedia
Silicon is a chemical element with symbol Si and atomic number 14. A hard and brittle crystalline solid with a blue-grey metallic lustre.

Silicone rubber is an elastomer (rubber-like material) composed of silicone?itself a polymer?containing silicon together with carbon, hydrogen, and oxygen. In its uncured state, silicone rubber is a highly-adhesive gel or liquid. In order to convert to a solid, it must be cured, vulcanized, or catalyzed. This is normally carried out in a two-stage process at the point of manufacture into the desired shape, and then in a prolonged post-cure process.

The presence of Silicon in an oil analysis normally indicates the presence of dirt, sand, and other like materials usually ingested into the engine through the air filter and induction system.

The Silicon in Silicone rubber is chemically bonded to the other elements, that is there is no free silicon. So running oil or fuel through a silicone rubber hose should not remove any chemically bonded silicon.
 
For the record, I measured the amount of oily residue in my catch bottle this annual inspection. It was only 10cc after 50 hrs. Not bad, I think. I guess I could have sent the residue off for analysis but I guess I don't really care.
 
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