I know my car stereo won't play a DVD data disc.
You need to use a CD -R as the data disc.
It will hold 7 to 9 commercial Audio CDs converted to .MP3s.
I've went past this as my car stereo can also use a USB flash drive up to 2GB.
I use a Micro SD card with a card reader adapter . This is very small . It usually takes me several days to listen to all of one card. If you are in your car for several hours a day it won't take you as long . Still several hours & you can carry several cards easily . It only takes seconds to change a card.