Another thing that occurred to me...a good percentage of more recent cars have hard drives built right into the radios.In such cars you can load your music right into the car’s radio and voila! Might your car have that feature?
I just replaced my car stereo, because the aux jack broke. I got one with a usb port. I LOVE using a flash drive. My mp3 player had to be recharged, so I was often without music. Wit the usb port, I’m always good to go, and I’m not limited to the memory size of an mp3 player.