Your car player may have in-let for media. Please check and if it has an inlet then you are luck, please connect the out-let from the mp3 player and connect the same to in-let of car player.
Hi
I'm renting a car soon and it has just a cd player(no cassette). Is there an adaptor out there I can use to play my portable mp3 player? I've looked on the net and can only find cassette adaptors.
Thanks.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic