The “proper” sound would be audio recorded by use of acoustic tube pre-amps/amps transferred directly to a vinyl record that could be played in the car haha.
But since that makes no sense to anyone, I just stick with nothing less than a 16bit 44.1kHz Wav / Aiff file. If I upgraded my system in my car that number would go to nothing less than a 24 bit 48kHz Wav / Aiff file.
AND by the way, you can’t get the above posted quality from shit sites like Limewire/Frostwire etc…