PURPOSE: To feed oil with a cap mounted on an oil filler port by forming aim insert hole for an oil feeding nozzle on the ceiling part of a cap, disposing an inner lid for closing the insert hole on the lower surface side of the ceiling part, and providing a spring member for pressing the inner lid to the ceiling part.

CONSTITUTION: A cap 11 includes a ceiling part 15 for closing an oil filler port 13 of a fuel tank and a connecting part 17 connected to the ceiling part. In this case, a hole 21 where an oil feeding nozzle 19 can be inserted is formed in the center of the ceiling part 15. An inner lid 23 for closing the hole 21 is disposed on the lower surface of the ceiling part 15, and the lid is connected to the connecting part 17 by a hinge part 25. Further, the coiled spring 27 is fitted to the hinge part 25, and both ends thereof are respectively pressed to the connecting part 27 and the inner lid 23. After opening an outer lid 31, with the cap 11 mounted on the oil feeding port 13, the oil feeding nozzle 19 is brought into contact with the inner lid 23 to be pushed in, whereby the inner lid 23 is opened to feed oil. On the other hand, as the oil feeding nozzle 19 is pulled out, the inner lid 23 is closed by the coiled spring 27.