I'm a recovering car nut and I used to use a product called "Back to Black" on plastic trim. I don't recall who makes it, but I think I have a bottle at home.

I've heard the stories about Armor All too, but I don't think that anyone claims that it does any harm to hard plastics. I've been using it since it first hit the market in the early seventies. I don't think I've ever harmed anything with it.