I thought you kept this car cherry, boy
I have been looking for this movie for so long that the only results on google are me asking about it....
Brian Dennehy (or someone like him) is a small-town cop, and he pulls over this young teenage-ish couple, and makes the guy get grease from under his car, and rapes the girl with it. He tells the boyfriend that if he turns around, and the cop is holding the gun, he will kill them both. But if he isn't, he will let them go. He isn't but the kid never turns around, and so the cop keeps raping the girlfriend. A line I (kinda) remember - "I thought you kept this car cherry, boy" - when making the kid get the grease. The boy and girl confront the cop the next day at some diner.
It is NOT Bad Lieutenant: Port of Call (before that) or that Stephen King tv novella about Ron Pearlman.
An old roommate and I used to quote this to each other in the mid/late 90s, so I know at least two people saw it, please help.