expression, godan verb (-su)
to oil; to lubricate
Used for applying oil to mechanical parts such as chains, hinges, or machinery to reduce friction. The expression is literal and concrete.
See also: 油を引く
自転車のチェーンに油をさした。
I oiled the bicycle chain.
ドアの蝶番
The door hinges are squeaking, so please oil them.