Oil

Oil is a flammable liquid that appears as a hazard in a few Mega Man games.

Mega Man 6
In Flame Man's stage there are oil pits that makes Mega Man slower when walking on them. If a Fire Telly or Fire Boy drops fire in an oil pit, the oil pit ignites to produce a raging inferno that, like lava, can kill the player instantly upon contact. Pookers can be used in one area to safely pass by oil pits.

Mega Man Powered Up
In Oil Man's stage, oil appears scattered in the floor in some areas. When Mega Man walks on oil, he will slip and fall, taking a moment to recover. If a Changkey Maker throw a Changkey in oil, it will ignite.

Mega Man 3 (PC)
In Oil Man's stage from the DOS game Mega Man 3, the oil dropping from pipes and drums harms Mega Man.