Hi folks, I searched this subject but am still wondering whether the oil fill cap is supposed to tightly seal the valve cover area or if it is primarily supposed to prevent oil from flinging out of the cover? The reason I ask, I am seeing a slight residue of motor oil around the oil fill cap. This oil residue appeared right after my last oil change and I think what it is is simply some extra oil that was covering the threads on the valve cover's oil fill cap opening. After the last oil change, I hand tightened the cap and I wiped down the entire area with a shop rag like I always do but I think that extra oil in the threads between the cap and the cover worked its way past the threads of the cap. So I was wondering if this indicates that the cap should be replaced or if it just indicates I should wipe excess oil off the threads prior to putting on the cap! Also, how normal is a slightly dusty oil residue around the PCV valve and the other hose coming off of the valve cover? Thanks as always.