Oil on plug threads… what could be the cause?

Hi all, doing my first plug change on my 08 CS with 76k. I bought it with a new short block done by Porsche under warranty at 39k back in 2014. I’ve only had for about 1000 miles. I already did the oil (0w40)and clutch/flywheel which was on its way out. Had Blackstone analyze the oil that was in it ( not sure how many miles were on it but looked pretty normally worn) and all was good. The second time out since my clutch job, I got the p0421 warm up catalyst efficiency below threshold bank 1 CEL. After talking and a little research, I figured all the banging getting the exhaust off knocked the prone to fail honeycomb loose. I have a Soul exhaust and the stock headers. I ordered some competition headers and figured I would call it a day. In preparation for the new headers, I figured I would change the plugs while I’m there. Pulled bank 1 on the passenger side first. Plugs 3 and 1 have oil on the threads, while 2 doesn’t. I haven’t made it to the other bank yet. My question is, is there anything other than bore scoring that could cause this?! Oil level was good before I changed it. After the change, it’s right at the top line on level ground cold. Could it be aos related? I’ll attach some pictures of the plugs and the analysis. Thanks in advance for any help!

Could it be the spark plug tubes? They have an o-ring on each end of them and one of them is right near the spark plugs . Sent from my SM-S908U using Tapatalk

Not sure. The coils were dry. Only the threads had oil on them.

So update, all 3 plugs in bank 2 had oil on threads.

That might be the remains of some anti-seize that a former mechanic used on the plugs. Porsche wants the plugs installed clean and dry. Also the gaskets on the first and last plug you show in the first group of photos - they don't look like the plug gasket has been compressed. The gasket should be fairly flat, the domed shape of these makes me think they weren't fully tightened. This can be the result of crud left from anti-seize in the threads in the head causing them to be harder to tighten, so they end up not fully tightened. If there was some oil dribbling in the plug tubes through the head it could travel down the threads. What I would do - and I'm NOT suggesting you do it - I may be a raging baboon with a wrench.. I would use my thread-chasing tap to clean the threads in the head (it's a special tap, NAPA would have one, that is not designed to cut any metal, it is designed to JUST fit the threads and clear any carbon out of them). I would then look down the plug wells with my endoscope (attached to my smartphone - about $20/ Amazon ) and see if there is oil dribbling into the plug wells. If there was oil, it's time to consider doing valve cover gaskets, so I'd be seeing my mechanic friend. If it was minor, I'd clean it up and press onwards.. I then would install new plugs with NO anti-seize. Zilch. NADA. Porsche doesn't recommend it, and most plug manufacturers actually recommend against it. The plugs are plated with a nickel coating that is designed to work as an anti-seize type barrier. Adding goop to it, in an engine that runs hot to begin with, it asking for trouble IMHO. So - that's what I'd do. What you do is up to you. Good luck! Let us know how this works out. BTW - those are some pretty shiny headers . I assume this is a track only car? No cats?

Appreciate the suggestion! The tubes seemed pretty clear. Just the threaded section had oil on it. no smoking on start up at all. I actually rented a bore scope to check it out, but it’s too wide and doesn’t have a 90 degree camera, so I can’t see the cylinder walls at all… This all came about because I was pretty sure my cat was going out. I just had the clutch and flywheel done 2 weeks ago, so all my fun funds were pretty low ha. I picked the headers up from TopSpeed in Texas. They were only about $400. Pretty impressed so far for the price. I have a Soul exhaust, so I picked up o2 spacers from them, so hopefully I can avoid CELs.

Here’s a closer look.

I'd love to see that photo with the oil wiped off the washer. Right now it looks like oil in the sparkplug "well" is the cause. The slight bit of darkness on the end of the threads at the active end is normal - just combustion byproducts. Your mixture looks perfect.

I’ll have to take another picture as all of the electrodes look pretty much the same.

BTW - just a comment. Your oil report looks just fine. If you had bore problems there would be for sure signs (like elevated aluminum readings) on the oil analysis. I think you can put that out of your mind as a concern.

Thanks for the positivity! I really hope so. Since there aren’t replaceable plug sleeves and o rings in the 08, could it be that my oil is just a little full and my aos could be pumping oil in the cylinder?

All of the electrodes and ceramic themselves look exactly like they should for a healthy running car. Tan/grey colored, with no oil wetness or burned or eroded electrodes. It will be interesting to see what your threads look like on the next change, as who knows what any previous owner or mechanic did of you aren't the original owner? You could even pop one out after some miles are on them just to see if anything is still there. Overfilled sump, or for all you know someone smeared oil on the threads a lubricant or anti seize. It sounds stupid I know, but Ive seen some strange stuff that people have done on used cars purchases of my own over the years.

That's a lot of oil, and its not dry or congealed at all, so my money is on failing o-rings on the spark plug tubes.

While they all look fine - was the one on the far right the one in the prior photo that I commented perhaps wasn't fully torqued down? It has been running very slightly hotter than the others, the electrode ceramic is slightly lighter in shade meaning it was running slightly hotter, that's usually caused by poor heat transfer to the head. The heat is transferred by the threads and the crush washer. If it wasn't quite as tight as the others this is what I'd expect to see. Still "normal" but just a bit noticeable.