PHOTOS HERE: https://imgur.com/a/YQxIKGd

I was changing my partner’s spark plugs last night and upon removing the coil pack I was surprised to see that spark plugs 3 and 4 had LOTS of oil in it.

Spark Plug well 1: no oil Spark plug well 2: a tiny bit of oil Spark plug well 3: so much oil that it almost covered the entire plug Spark plug well 4: lots of oil, covered about half of the spark plug

She said she was getting rough idles about a month ago, around when the temperatures started dropping. Then last week she got a check engine light. I used an obd2 reader and got a P0300 code for a cylinder misfire, which is how I came to the idea of replacing the spark plugs.

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Context:

• 2012 Chevy Cruze
• 180,000km / 111,800 miles
• spark plugs had never been changed in the past
• P0300 code
• pictures of spark plug wells and old spark plugs in the link above

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I’m thinking it might be the engine valve cover or engine valve cover gasket that’s leaking into the spark plug wells.

Before I go and buy new parts, does this seem like an accurate assessment? What else could it likely be? And can I just replace the gasket or is it a good idea to replace the valve cover as well? Could I just replace the gasket, see if that fixes it before replacing the valve cover or should I just do them both at the same time.

Thanks so much for any help!!!