Do you need to know how fast you're going? Yes.
Do you need to know how your car is performing? Yes.
Do you need to know where you are and where you're going? Yes.
We already have head-up displays that show car parameters, as well as navigation systems that help you get where you're going. This could be incorporated in to an HUD ("turn here ->").
Anything more would be information overload. I do not need ads to tell me how cool the store I'm driving by is (i.e. how much they paid for the ad), nor do I need neat pictures other people have taken in the vicinity.
Look at how they do it in airplanes: the pilots have the essential information in front of them, but can access other information as needed.