Is There A Temporary Substitute For An Oil Filler Cap?

Plastic baggie w/ rubberband over it?

Find/make an appropriately-sized stopper?

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You can find something like this in the right size and use it forever. Find a place to connect the chain and you might keep it forever, too.

- gpsman

Aluminum foil? I don't think there's any pressure behind it...

No sir. Oil is all over the garage floor after the mowing session. The only possible exit from the engine must have been thru the capless oil filler hole.

Is it the '24 755 46-S' on the Kohler CV12.5-1215 engine?

This will substitute pretty well:

--Winston

I thought that the fill cap was on top?

If there is oil showing on the floor, would you think maybe something at the bottom is leaking?

On the other hand, maybe the CIA is doing brain control experiments, and you're the victim of a psychiatric mower inverter ray. They do it between 3 AM and 4 AM. But, you can block the ray by stapling aluminum foil to the inside of your garage, shiny side out.