Some years ago I got a spike in silicon and copper in oil analysis. It was posted here in
various threads related to oil analysis. It turned out to be a little gap, about 3mm, in the alternate air door, allowing soil ingestion (the silicon) and causing excess wear of soft metals (copper and others).
Quite funny to get one of Savvy’s business promotion circulars mentioning exactly this problem
Whenever we see elevated iron, the first thing we ask ourselves is “was this engine inactive?” Steel cylinder barrels almost always rust during periods of disuse—particularly in humid climates like the DFW area where Jay is based—and that rust scrapes off when the engine is run and shows up as elevated iron in the next oil sample. Jeff asked Jay about this, and Jay admitted that the airplane had been down for a month and a half for its annual inspection and then sat awhile longer while a new GPS navigator was being installed in the panel. That seemed to explain the elevated iron.
But what about the elevated aluminum, chromium and nickel? Disuse couldn’t explain those. What could cause all three of those wear metals to spike simultaneously? The most obvious thing that could do exactly that would be dirt in the oil, because dirt turns oil from a lubricant into a grinding compound that invariably causes all wear metals to rise.
Sure enough, the March report showed silicon at 15 ppm, about three times what it should be. No question that excessive amounts of dirt was getting into this engine, and that certainly explains why all the wear metals went up.
How did dirt get into the engine? While it could be a bad induction air filter, our experience is that the most common cause of dirt-in-the-oil syndrome is a carburetor heat or alternate air door that isn’t sealing properly, allowing the engine to breathe unfiltered air. This is the sort of problem that can go undetected for months, even years, unless the engine is on an oil analysis program and somebody notices that silicon is elevated (usually along with a bunch of wear metals).