I'm guessing the
oil is wicking in at the valve cover to gasket and spiraling up the stud.
Stat-o-seals work great for bolt leaks but I'm afraid they won't work on the studs (need a smooth shank area to seal).
https://www.parker.com/literature/Se...CSS%205125.pdf
Parker does make a Thread seal version that MSC stocks.
https://www.mscdirect.com
https://www.mscdirect.com/product/details/65075848