My 2015 Rubicon has 187 miles and 38 hours on it. I went to replace the spark plug with an Iridium NGK version and I noticed some black carbon deposits on the plug. I then wondered if the top of the cylinder might look the same and sure enough when I stuck a bore light down the hole it was caked in solid black.

Is this normal for such low mileage/hours? Is there anything to worry about? Is there a way for me to clean the cylinder? What would be causing this? I’ve been using good gas (87 Octane from Shell) and Honda oil.