The Silicon Bugaboo
Stating that the element silicon – when it appears in the spectrometry of oil – has one source and one source only: abrasive dirt.
That was wrong.
Many people believe silicon only comes from dirt. That point of view is so firmly set that laboratories using only computer-generated comments often state that high silicon is from abrasive dirt and do not take into account the many other sources of silicon (additives, sealers, etc.).
Neglecting to take into account the other potential sources of silicon in an oil is as much an error as the gentleman expounding on silicon in our lobby.
In oil analysis spectrometry we look at elements rather than molecules. When we read any element, we can only assume the molecular form from which they came.
Here are several items that can cause high silicon readings in an oil sample. Some forms will harm an engine, and others will not.
Silicone-based gasket sealers (red, blue, or clear) used in engine assembly and repair, show up as high silicon in an oil sample. Any oil sample taken from a new, rebuilt, or repaired engine typically reads high in silicon.
Oils from some types of new engines may read as high as 400 ppm silicon. You can ignore the high silicon in these cases since it is harmless and will wash away by the third or fourth oil in the engine.
Aftermarket oil additives often use compounds that will leave silicon reading high in an oil sample. There is a compound for instance, used in anti-foam additives, that can run silicon up to as high as 70 ppm. This form of silicon will not affect engine wear.
Silicon often reads high in an oil when coolant seeps into the oil system. It comes from silicon (rust) inhibitors used in the anti-freeze. While the inhibitors aren't necessarily harmful, the anti-freeze certainly is, and you will want to seek repairs before the engine is seriously damaged.
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.
Analysts consider all these factors when making recommendations about the condition of your engine. The more information you give us regarding any additives used, rebuilds the engine has been through, or any other special considerations we should take into account, will help us determine the true health of your engine. We can then make appropriate recommendations to help you prolong its life. And in the end, that's what it's all about.