Why fluid found in spark plug well?

I’ve changed dozens of plugs over the years with no problems but this time I noticed that all of my 97 Odyssey spark plug wells contained ~1/4" of dark oil in the bottom. I always torq in the plugs so sure they were not loose. The only difference is that the last time I used NGK ZFR5FGP plugs, which didn’t need to be gapped. The electrodes were point like, which I think is how they came.

Car has performed well over since I put these in 2.5 yr and 21K miles ago, but does this oil mean something?

Most Cars With Plugs In Wells, Have Seals Or O-Rings Around The Wells (Tubes) That Keep The Valve Covers From Losing Oil Into The Wells. Your’s May Be Leaking A Bit. They May Need To Be Resealed.


It’s not really a problem unless large quantities of oil are getting through (i.e. enough to drip into the spark plug hole when you remove the plug…) If that’s not happening, I’d just leave it alone.

I see an opening around the top of the well. Is that where you mean the O-ring may be leaking? Would that make sense for all four wells to have accumulated oil?

The oil would definitely leak into the engine if the plug is removed. I spent some time with Q tips and paper towels laboriously blotting up the oil before I removed the plug.

In that case you should be able to have a trusted local mechanic remove the valve cover and replace the O-rings. Easy job.

It’s also possible that just re-tightening the valve cover nuts would stop the leak. You could try that first.

The O-ring is at the bottom of the well.