Engine oil filler cap screws into this hole in the rocker cover. I noticed the threads in the hole have three colours red which is the paint, silver which is the bare metal and also another type of dark n dirty but solid surface that doesn’t wipe off. What is it, does it need removed and if so how can I remove it? You see less of the stuff from top but there’s more inbetween the threads which the camera could only get a blurred pic off.


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all that is, is just gunk or dirt or very possibly even oil that was on the cap and wedged in those grooves and has been heated up and cooled down over and over causing it to solidify. What you can do is take a paper towel and very carefully wipe the threads and see if it comes off. try avoid getting any in the engine itself.

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    Given the OP's track record at car DIY, I would strongly suggest leaving it alone. Otherwise (with no disrespect intended) the next question might be "I accidentally knocked a cup of water and detergent into the hole while trying to clean it. I then tried to soak up the mess with paper towels but they disintegrated and finished up inside the rocker cover. What do I do now?"
    – alephzero
    Sep 28, 2021 at 18:56

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