A midnight rave is, when you are having sex, you abruptly turn off the lights and crack a glowstick(s) on your partner's genitalia, using it as lubricant.
"damn! Johnny gave me a midnight rave last night, I was so surprised, my vagina is still irradiated!"
"I surprised Katie with a midnight rave and my dick is still sizzling"
Noun. Midnight oil means male semen. Comes from the fact that male semen is ejaculated usually by nighttime in shadily fashion and from its thicky, oily appearance.
You better watch your back, Annabelle. That guy is always ready to inject some midnight oil into unsuspecting p****es.