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Acura with oil on spark plug threads ? Worthy of concern?

I have a 2013 Acura RDX AWD with only 39k miles on it. At idle, it had a very slight stumble once in a while, so I thought I’d take a peek at the spark plugs. Much to my surprise I found oil on the threads. I’ve never seen anything like this on any of my previous vehicles. The tips of the plugs were dry, however. My 2010 TSX has twice the miles and the spark plugs come out bone dry. Should I be concerned? Is this worth bringing to the attention of the dealer service department? Warranty ?

Read your manual concerning warranty coverage and yes have it looked at before any serious damage might occur.

Is this wet oil on the threads or a crusty black burned oil?

Wouldn’t this be from leaky valve cover gaskets? It has a 50K bumper to bumper but not sure if gaskets would be covered. I wouldn’t doubt it though so I’d have a discussion with the dealer on the stumble issue. My experience is that they pretty much cover everything for 50K.

Seems a little crusty and burned, particularly toward the end of the threads. I’ll take a close look tonight. Btw, the original photo is the rear bank, attached is the front bank. I haven’t noticed any unusual exhaust emission.

Thanks so much for the reply.

A gasket is starting to make sense to me. I have no evidence of external leakage, and no evidence of oil burning in the exhaust emission. Thank you so much for the reply.

If the dealer’s tech doesn’t see any oil in the spark plug wells there is no reason to reseal the valve covers. Those spark plug look rather clean.

Is this a city car? 39K on a city car can be equal to 150K on a country car.

Please clarify; are you saying there is liquid oil on the threads?

Well worn plugs, number 2 first picture is a concern, so fouled, yes time for a real mechanic to take a looksie.

Have you owned this since new?

Car Talk Lacke:y

time for a real mechanic to take a looksie


It has a 50K warranty so needs to go to the dealer at least for a look.

Those plug gaps look sort of bigger than I’d expect. Maybe that’s the norm w/newer cars, but neither of my vehicles have plug gaps that wide. Did you measure them, compare to what it should be? Too wide of gap can cause misfires and pinging. Can also damage the coils. Other than that, this is not something I’d worry about. Oil gets pretty much everywhere, more and more accumulates as the years go by.

The gap may look unusual because of the pointy iridium tips. Iridium spark plugs wear so slowly they look the same as the new plugs after 120,000 miles.

Not really, just slightly crusty and burned.

Just trying to get some opinions before I go to dealer, so I’m ready for the usual “oh, that’s normal” B.S. from the service manager. Thanks to all for the replies.

Then they look fine to me. Throw in a new set and motor on.

Sorry if you think this is BS…



The crud is darkest near the business end of the plugs, so it’s coming up from the combustion chamber, not from the valve cover end.
And yes, it’s normal. Every plug I’ve pulled has some of this.
metal threads do not make a completely gas tight seal.
Here’s a plug I recently pulled from my Toyota Matrix at 58k miles:

The fibers on the left drifted in on the wind.

Yes. The crust is from combustion and it’s normal. Replace the plugs with the same brand that came in it then check your dipstick, tire pressure and coolant level and if all else is good smile and drive on.

edit; also, have the plugs been removed and reinstalled in the past? doing so weakens the sealing rings and worsens the leaking of combustion gas past the threads. If it is necessary to reinstall old plugs that use sealing rings those rings should be replaced.