These were in the car for about 10k miles. They were very easy to remove-one was loose enough to remove by hand. They all have gray-ish gunk (oil?) in the threads except one. There is a little oil on the top white parts too. The business ends look good except for one which has much more buildup on it (the same one with fairly clean threads.) Something isn't right here. Can anyone lead me in the right direction?
The one with cleaner threads/most buildup:
The one with cleaner threads/most buildup:
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