Check to make sure there is no fuel in the tank before removing the oil.

To remove the oil, tilt the mower on its side and pour the old oil into a proper container.

Alternatively, you can use a siphon/pump down the opening to remove the oil.

Never pour engine oil down the sink. Put it in a sealed container and take it to a proper oil recycling or waste disposal facility.

If using the tilt and pour method, ensure there is no fuel in the tank, as it may leak out.