Poor Man's Process - still works, after all these years.
https://www.youtube.com/watch?v=AYdfMYrfB7s
Yup, that's how it's done........
A little more context will help.
I've done audio post on all sorts of "in car" scenes. Shooting in a real car introduces all sorts of nasty sounds to the production sound track that are not easily removed. My "favorite" are scenes shot in a stationary car (with people to rock it occasionally) as the dialog is always pretty good and I can create any soundscape needed rather than trying to work around crappy production dialog.