About 18 months ago I bought a new oil drain pan - one of those flat plastic jug kinds that holds the drained oil securely until you can take it to the recycling center. I dutifully put it underneath the engine, opened up the cap in the middle of the drain area, uncapped the vent, then finished unscrewing the oil drain plug on the bike. The oil poured out, as expected.
But - and I couldn't believe it at the time - the oil didn't go down into the jug. It pooled up on top, and then started overflowing onto the driveway.
It turns out I the air vent hole was not actually a hole - it was covered with some leftover manufacturing plastic. I rammed a screwdriver into it to clear away the hole, and magically all the oil that wasn't already on the driveway burbled happily into the container.
It took a bag of kitty litter to clean up the spillage. And I discovered that Nitrile gloves will keep your hands clean, but don't protect you from really hot oil.