I have 20 years of SOS reports on my 3116's and everyone has water and fuel contamination reported as "N" which is none. Just for reference sake, the last SOS was done with 150 hours and 1 year on the oil, but total time of 1550 hours on the engines and the contaminents were
Chromium 0 ppm
Aluminum 1 ppm
Iron 4 ppm
All were within normal limits, according to Thompson Caterpillar in Nashville TN
Since I've never had a report come back with anything but "No" fuel dilution, I've had to do some homework on that,
Fuel contamination is measured and reported as a % of volume. So an engine with a 26 qt. oil capacity with 1.0% fuel dilution means the engine is holding roughly a 8oz glass full of fuel when it should have <.2% fuel contamination. So, my view is that a 1% fuel dilution isn't the end of the world, but coupled with abnormally high Fe, AL and Cr, it is indicative of a cylinder wash out that can get very expensive, and in the worst case, end up in a top end overhaul which on a 400/410 or 380DA (guessing) means removing the cockpit deck and the offending engine then boring the engine and sleeving the cylinders and buying a new set of pistons and rings.
The low run time but all done at idle could be the cause of the problem if one or more cylinders was not completely burning its fuel charge. To determine that may take removing the injectors and having their spray pattern tested on a test stand. That would requires resetting the overheads when the injectors are reinstalled.
The more I think about this the more complicated the route to the finish line becomes.
Frank
You’re a wealth of knowledge Frank. Thanks for taking the time to write all of that up