Richard has downloaded the TuneIn app, where he downloads podcasts and then listens to his phone. His stereo system doesn't support the mp4 stream, though. Leo says it shouldn't because mp4 is video. He can save audio as that, but it's not very widely supported. He'd have to reencode it to listen to it.
Leo advises just streaming it live. That way the phone can handle the encoding, not the car stereo. Leo also suggests going Bluetooth instead of the USB connection, if he can.