If your car is old enough to have a tape deck, they have cassettes that connect via Bluetooth. Just about perfect sound quality since there is no interference.
I changed cars in January and the car I previously drove, an 05, Jetta had a tape deck. I bought this to connect my phone. Surprised that it handled calls as well.
Yeah those worked way better than the fm transmitters. Only problem was my car introduced a humming sound into the signal that got worse with speed lol.
It's not the radio that didn't work. These were fm transmitter/receivers you used to play mp3 players/cd players back in the day when vehicles didn't use aux cables. It sent the signal over short range fm signal to your radio.
The alternative was the cassette adapter, but some vehicles had swapped to cd