Dumb question: Is there a quick test I can do to rule out (or in) fuel dilution in the oil? My genset crankcase seems a bit high, but maybe I just over-filled it at the last oil change.
If you've got some thick uncoated paper, some clear plastic, and/or a magic 8-Ball, there are some things you can try. Unless the results are truly profound, it is usually much easier to compare the same engine to itself over time using the same paper type, or, at the least, to compare one engine to a sibling engine using oil of the same type and age.
Start out by just looking at the oil. Does it look and feel like normal? Does it smell like normal. If it is "milky", there is a huge amount of coolant or water. If it smells like diesel, there is a huge amount of diesel.
If you look at the dipstick and see balls of water, this is obviously a bad sign.
You can put some onto a piece of clear plastic and shine a bright light at or through it. The dirt should be fine and uniform. If it granular, it might be the casethat water or coolant has been getting in, pulling the soot into balls, and then evaporating.
If you look at it and it isn't as dark as it should be for the hours, then something is up.
If you take some thick uncoated paper, i.e. paper without any gloss or special treatments and put a drop of oil on it, you can sometimes get a sense as to what is going on based upon what you see in the oil and the way it is absorbed and makes rings. Some people use cardstock for this. Some people use back light. Some people use a magic 8 ball. This is much more art than science. Look at it both with light shined at it, and with a super bright light shined from behind.
If you see a dark blob in the center but a wide muddy ring forms around it, there may be a lot of water in the oil. The water will spread through the paper faster, bringing some dissolved dirt with it.
If you happen to spot a wide and slightly lighter oil ring around the spot, but one that is still oily not dirty and wet, you are a magician. You found a ton of diesel in the fuel.
Some people claim this works better with paper towel than thick paper, but i usually just get a soggy mess. Maybe I'm not buying good enough paper towel.
Again, this type of blot test, except when comparing an engine to itself at the extremes, is more of an art than a science. And, it may be more psychology than science -- akin to an "ink blot test"
