Changed my spark plugs last week and all of the plugs seems consistent and normally worn except this one. It has a little bit of oil on the thread near the tip and has more carbon deposits than the other 5 plugs. Plugs have 100K miles on them. This "bad" plug is the front most one on the passenger side. Should I be concerned? Car drives fine.

 

It's burnt time for all 6 new ones not just that one check coils inside to make sure there isn't any burn

 

If the coil isn't misfiring, that cylinder looks to have poor ring seal. Could also be an intake valve seal failing. It doesn't look like excess fuel.

 

"Burnt" it's really a meaningful description. What you are seeing there are oil deposits, which means oil is getting into the combustion chamber and burning. This can be caused by oil leaking through worn valve guides or piston rings, but it doesn't have to be anything so dire. The front most cylinder would also be the one getting the majority of what is coming through the PCV valve on its respective side. Try checking the PCV valves to make sure they are clean and that there isn't any oil pooling in the channel behind it in the valve cover. A blocked PCV could also cause more oil to be forced past the rings.

Does your car burn any oil between changes? Do you have any smoke from the tailpipe (you might need to have someone stand behind you when you start the car and drive behind you while you do a few runs). Report back with your findings.

It's time to replace all 6 plugs regardless, but you need to fix the mechanical issue that is causing the oil deposits first.