Potion of oil

The potion of oil is a potion in Nethack with cost of 250.

Quaffing this potion is not useful and in fact abuses your wisdom. It has other uses, however. One use is to untrap a squeaky board, similar to a can of grease.

The other uses involve lighting the oil by applying the potion. A lit potion of oil is dangerous when quaffed - it deals fire damage and abuses wisdom unless you are polymorphed into a monster that likes fire (note: this is not the same as intrinsic fire resistance). A lit potion of oil can be thrown at an enemy to cause some damage; no damage is incurred if unlit.

Oil can also be used to fix damaged weapons. By dipping a rusty or corroded weapon into a potion of oil, it loses one damage. To completely repair a thoroughly corroded weapon, you thus need three potions of oil: from thoroughly corroded to very corroded to corroded to uncorroded. Oil does not repair rotten or burnt weapons.