Engadget
Android Auto YouTube Limitations: Is It Worth Using In The Car?

Google announced that Android Auto will gain native YouTube support later this year, allowing HD video playback at 60 fps while the car is parked and automatically switching to audio-only mode when driving. The feature requires a YouTube Premium (or Premium Lite) subscription, and current implementations only stream audio with limited controls. Unofficial apps can already show video when stationary, but they are not officially supported.