noun
lubricating oil; oiling a machine
Refers both to the oil used for lubrication and the action of applying it, especially to machinery or moving parts.
ミシンに差し油をさした。
I oiled the sewing machine.
自転車のチェーンに差し油が必要だ。
The bicycle chain needs lubricating oil.
潤滑油 is a more technical term for lubricating oil, while 差し油 is a common, everyday word often used for small machines or household items.
Compound of 差し (sashi, the continuative form of 差す 'to insert, apply') and 油 (abura, 'oil'). The exact historical derivation is uncertain, but the word transparently means 'applying oil' or 'oil for application'.