Push in oil cap that actually seals.

[Lynn]

What is odd is that there is a push in cap on the other side. It has never leaked.
This is my third one on this side. Holes are the same size and there is no distortion or rough edges. I ended up putting a freeze plug in the oil fill tube hole in the manifold because it interfered with my upper radiator hose. If there is a rubber freeze plug that fits I may try it. Although, I am wondering if the rubber in the freeze plug will stand up to oil.