vinyl

I treat vinyl and leather like skin. Only cleaner I use on either is the crème type Gojo hand cleaner with lanolin in it. Am I saying I would use a similar hand lotion on the headrests ? yep
Keep in mind that the only proof I have of my success is a OEM 67 dash pad.
It's not shinny as if it had armorall on it but it isn't brittle either.
Also note, This is a periodic treatment over the years as protective measure and not a hale Mary effort/effect like you're looking for.