burn midnight oil 

to stay up all night doing work. often homework.

i burned midnight oil last night but slept in coz i was too tired

burn midnight oil by yo April 15, 2004

burn the midnight oil 

to work diligently, especially late into the night

I had to burn the midnight oil to get that done.

burn the midnight oil by The Return of Light Joker March 26, 2009

burn that midnight oil 

A clever way to ask your 420 friendly fuck buddy to come over late at night, do some dabs, and fuck like rabbits.

Similar to Netflix and chill.

And. . . It doesn't count if you're just smoking weed. Dabs only. kk?

Guy: Hey what r u doing?
Girl: Not much, just bored :-(
Guy: You wanna come over and burn that midnight oil?
Girl: Ummmm. . . Sure. . . why not? I haven't been high all day ;-)

burn that midnight oil by DoctahGonzo April 25, 2016

burn the midnight oil 

To stay up all night working. Apparently some drop the "the", though this must be rare.

Man Bob, you must have really burned the midnight oil on this one!

burn the midnight oil by ManyTreez May 29, 2005