Examples
- I burned the midnight oil all week to finish my dissertation on time.
- If you plan your revision properly, you won't need to burn the midnight oil before every exam.
- The whole team is burning the midnight oil to fix the bug before the app launches.
How to use it
Neutral to informal. Usually about a period of hard work, often with a deadline.
Where it comes from
From the days before electric light, when working late meant burning oil in a lamp.