First welcome to the MMI Forum.
Looks like a sender possibly. Is the narrow end an electrical plug or a slip fitting?
The oil pressure sender is usually mounted on the flywheel end. It could also be an oil pressure switch for an electric fuel pump if so equipped.
It is screwed in at an oil galley access port. All we need to do is figure out what it is for if it is a sender. If it is a slip fitting for tubing it could of been hooked to a mechanical oil pressure gage.
It can be replaced with a standard NPT pipe plug to address the leak, then you can figure out what it was for later. Use a bronze plug if you can although any NPT plug will work temporarily.
Dave Neptune
