Understanding Oil Contaminants

I recently received a question about silicon contamination results asking how silicon gets into oil and what can be done to prevent future recurrences. First we need to understand what silicon is and where it comes from. Being the second most abundant element on earth after oxygen there are numerous sources of silicon contamination. Silicon is commonly found in dirt, sand, dust that enters motor oil through air filters, defective air induction systems, leaking seals, loose oil fill cap or dipstick seal etc. Therefore most labs analyzing oil samples will recommend changing oil and inspecting air intake system starting with air filter, then checking for leaks in intake system by blocking air intake which should either cause engine to stall or create a sucking sound at leak point. Common leak points are loose clamps at hose connections or cracks in hoses, manifold or air filter housing. While the majority of silicon contamination issues can be corrected with a simple inspection and repair you may have less common causes including aluminum wear as most aluminum alloys contain silicon or anti-foaming agent additives in newer oils that contain silicon. If your aluminum wear is increasing at 3 to 1 ratio with silicon chances are it is coming from a part that contains an alloy that contains silicon. If you recently changed brand of oil and silicon is higher than previous samples contact oil manufacturer or perform a new oil sample to determine starting silicon level before taking any action. Also it is imperative that you review your oil sampling process to ensure the oil collection was taken from a clean valve or oil retrieval tube and didn’t dump sand or dirt into collection bottle.

I also ask those who have a drastic increase in silicon if there was any recent engine work performed that could have added silicon to system. For example if a new cast part was installed it is possible that the sand blasting material was not properly removed, Or if head was changed and sand paper was used to remove old gasket or technician simply allowed dirt to fall into engine when head was removed etc. The use of a silicon sealant would also add to silicon level if oil came into contact with sealant before it properly dried.

A silicon reading higher than 20 PPM usually will trigger an oil change and recommendation to perform inspection to locate and repair the point of contamination entry. Take a few minutes to review recent maintenance or oil brand changes before taking any costly time consuming actions.

If you truly have a dirt, sand or dust issue you will see increases in wear in upper and/or lower end of engine that will be identified by wear metal combinations by the lab. Air filters and quality bypass oil filters (that function properly) will usually trap and prevent any particles from getting lodged in tolerances causing excessive wear, but there is always the possibility of contamination occurring elsewhere. If you do not have the oil analyzed regularly silicon contamination will go undetected until a routine engine teardown or failure occurs. The cost of an oil sample is money well spent as the knowledge of engine health will improve overall maintenance decisions and avoid high $$$ unscheduled repairs.

If you have any questions or topics for this column please email me at: [email protected]