How do I connect my watch to my car?

Why do you want to connect it to the car? Do you want to play music from the watch? It should connect as any speaker.

When I get a call in the car it's coming through my watch and disconnecting my phonecall. Maybe I just need to disconnect my watch for calls??

Are you connecting the phone to the car?

I guess both the watch and the car will act as handsfrees which probably will not work any good. The watch is connected first and will probably take priority over the car. 

I read that the bluetooth device that is added the last will have priority over older devices. That is what I would try first. Make sure you add your car last. So, remove it as a bluetooth device in the phone and add it again so it is the newest.

I tried to find how to set the priority and there are several apps that claim it can do it. I haven't tried any so I can't give any recommendations.