Oil Analysis- Silicon Readings

[acts]

I have been digging for information on this site and on the net. I'm surprised at the lack of information, other than to conclude automatically that silicon means dirt. I've read the air filter debates as a cause, as well as whatever oil analysis debates were available.

Blackstone Labs is the only place I found a situation that represents mine. They have a specific article on their site named the "Silicon Bugaboo." They explain that high Silicon readings are commonly caused by our sealants and gaskets that contain silicone. They even provide specific ppm ranges. They explain that their oil analysis/spectroscopy only sees Silicon in elemental form as a whole, not at the molecular level to discern specific origin.

After purchasing an older RV4 with a higher time IO-320 engine, I've run 3 samples about every 25-30 hours with AvLabs and the last two have shown high Silicon readings (18, then the last one 16 ppm) when it should be more commonly somewhere between 4-7 ppm. The first analysis showed 5 ppm. This change occurred right after I replaced the 10+ year old thinned out silicone gaskets for all 4 valve covers with brand new silicone gaskets. All the other metal analysis findings are within normal limits and show no trend of increase. The oil filters have all been perfectly clean.

According to the Blackstone write-up, "There are certain types of gaskets used at pan and valve cover areas that are made from silicone-based materials. If these are installed on your engine, you can expect the silicon reading from your oil sample to go up to 15-20 ppm and continue reading high for as long as the gaskets are in place." This of course places my findings directly after silicone valve cover gasket replacement- right in line with that statement.

With all the discussion on the importance of oil analysis to mark trends on the health of your engine, as well as all the discussion of the importance of maintaining low Silicon levels for your air intake/fuel system health, and all the discussion on how much better the silicone valve cover gaskets are vs the cork gaskets, I would have guessed that I could easily find others affected by the combination of results.

Anyway, I'd appreciate any feedback, and hope that maybe this sheds a little light on a rather dim topic (at least from what I can see) that may have been noticed by others.

James

P.S. As an additional measure of caution, I'm changing out my K&N air filter as well, after reading posts on shrinkage and the filter element getting holes after "X" amount of time (although it appears in pretty good shape and seals nicely). I have used the K&N recharge system and its instructions under the guidance of an AP/inspector as well as a 40,000 hour/multiple RV builder pilot during the first 2 annual inspections.

[JonJay]

I am not a big fan of oil analysis for the exact reasons you have written this. Perhaps if you are running a fleet of engines I might feel differently.
In my limited experience, Lycomings tell you early, and often, when there is a problem before it escalates into something causing a major repair.
I know this isn't helpful and does not answer your questions. I also know there are others here that are in the other camp.

I would not spend too much of your time chasing anomalies like this, but that is just me.

[hohocc]

I heard a similar story years ago of an aeroplane that lived around the central north island in New Zealand, where much of the soil is of volcanic origin.
The cause was narrowed down to the owner checking his oil level, and not having a rag to wipe the dipstick he'd wipe it in the grass to get a clear oil level reading. The soil type was very high in silicon causing a jump in the oil analysis results.
Probably not what's happening to you but worth passing on.

[ArlingtonRV]

I have the same situation with a 1997 RV-4. It has an O-320 originally from around 1975. The cork rocker cover gaskets were leaking and I replaced them with the orange silicone ones from Aircraft Spruce. On my next oil analysis (Blackstone) I got the spike in silicon and a warning to check my air filter.

I had, in fact, just replaced the filter a couple of months before taking out the old one with a chunk cut out and RTV squirted around the accelerator pump bulge as per earlier Van's instructions with a different P/N K&N filter that will go around the accelerator pump without being cut into. I now have a good tight seal to the bottom of the carburetor, so I knew that wasn't the problem.

I responded to Blackstone about the silicon valve cover gaskets and they agreed that was likely the culprit. Right after changing them the level spiked to 27 and has been gradually coming down (27, 12, 10) in subsequent samples.

I send a sample every other oil change and only use it for trend analysis, not to spot acute problems right away.

In my case I feel that I know what the cause is and don't worry about it too much.

[60av8tor]

I, too, had Blackstone report silicon spikes in a couple samples following gasket replacement. All is back to normal now.

[Doug]

Isn't this a good thing? Confirmation that the lab analysis is sensitive enough to pick this level of contamination. If the number is low you can be sure it is ok - if it is otherwise then further investigation is required.
Thanks for shareing - re-afirms my practice of getting a sample tested at every oil change.

[CharlieWaffles]

Weird, I just got my my recent oil analysis back and they flag the silicon as being higher than last time (20ppm). Wasn't an alert, just a not about watching elevated silicon levels.

[terrykohler]

Several years ago, high Cu on my new engine lead me to contact a factory engineer at Lycoming. Learned that they copper flashed their cams (the flashing is then polished off the bearing surfaces) to allow selective case hardening of the lobes. The remaining copper is left on after heat treat - no real reason to add cost of removing it. However, some additive in the Aeroshell was slowly stripping off the remaining copper. No big deal, but it certainly got my attention as my first thought was premature bearing wear.
Terry, CFI
RV9A N323TP

[tim2542]

Good info thanks. Just wish I had learned this before I spent $50 on a new K&N. My Silicon #'s are right in line with yours and...silicon gaskets.
Tim

[RV7A Flyer]

Originally Posted by terrykohler

Several years ago, high Cu on my new engine lead me to contact a factory engineer at Lycoming. Learned that they copper flashed their cams (the flashing is then polished off the bearing surfaces) to allow selective case hardening of the lobes. The remaining copper is left on after heat treat - no real reason to add cost of removing it. However, some additive in the Aeroshell was slowly stripping off the remaining copper. No big deal, but it certainly got my attention as my first thought was premature bearing wear.
Terry, CFI
RV9A N323TP

How high was it, if you can remember?