Nearly every automobile MP3 player (USB-based or CD-based) I've used was defective in some way. Usually something stupid like only playing tracks in alphabetical order, or inserting audible gaps between tracks that are meant to flow into one another, or not supporting tags correctly, or not handling UTF-8 text... Car companies don't know how to do consumer software.

Mine would cut the last few second and first few seconds of each song with some terrible "meld together" business, like the world's worst DJ.