Oil on spark plugs, what could be the issue?

[ZDA3]

Upon removing the old spark plugs to replace them with new ones, there was some oil on the old spark plugs, but just minimal.

I noticed upon removal of the old spark plugs that it wasn't as tightly screwed on, but it wasn't loose either, could that be the reason or something else?

2014~2018 Mazda3

 

[Silly Wabbit]

Wet oil or dried stains? Pictures?

 

[ZDA3]

It was wet, but minimal, like barely a drop. The 3rd spark plug/ignition coil boot was more wet than the others but not dripping wet.

Sorry no pic of it as I already installed new spark plugs.

 

[ZDA3]

I guess first line solution is to replace the valve cover gasket?