Or you could use the USB to play music from Spotify on your car. To do that, you will need to use a Spotify MP3 Converter to help you get Spotify music to USB cause Spotify music files are protected. After then, you can play Spotify music via USB on the devices you like.
It's easy to use Spotify through the system via Bluetooth. Here is a detailed tutorial on how to play Spotify in the car via Bluetooth.
Besides, you can also play Spotify through the system via the USB port, as almost all cars have a USB port. You just need to use Spotify Downloader to download and convert Spotify music to common audio files and transfer them to USB. And then all things could be OK.