Display contact information for each car owner
How do you gather the contact information? Is it profile fields or a node connected to the user account?

Regardless of the method you can create a view that will use the author of the node as the argument of the view (D6) or contextual filter (D7) to bring the contact information for the user. One thing to consider is that you might have to create a relationship to the entity or method you used to collect the information.

After the view is created the next thing will be to decide how to present it, maybe you want to create a block, or attach it at the end of the car content type or make it a tab, all those options are available in views as well.