That I’m not sure about. My son works at an amusement park and the water stays cool while it sits outside (he also drinks it at regular intervals) but in a hot car… that’s another story. My *guess* is that it will be cool. Sorry I couldn’t really help.
4 hours, with ice, for sure. Since you mentioned your car, I’ll also say that mine leaks a little when I shake it so you might want to watch how it’s placed. (I’m not sure if the bottle came with the minor leak or if the lid had been put through the washing machine when it shouldn’t have.)