Welcome to the forums!
Hope you're still with us, I found your post buried elsewhere getting no attention.
You may be able to connect your phone via USB and when prompted, choose the Disk Drive connection.
If your car stereo can read a simple Windows-type SD card (many can) you'll be able to navigate thru your music folders and select songs for playback.
Guess that will depend on your car stereo model.
Hope this helps!