Define Changin' The Oil Meaning

Drew: Jesus fuck I'm bored
Mikey: Me too
Drew: *Exits room and locks self in room*
Mikey: The fuck are you doing in there?
Drew: Changin' the oil
Mikey: that reminds me, i haven't had an oil change in almost 24 hours.

“Hey man, you used to get right ripped with us. Since you moved to the city, you’re Changin’ Gavrilo’s Oil, man!!!”

“Ah darn. You’ve totally caught me.”