Honestly, it seems like a lot of people put the car out of center just to have the car out of center. I don't see that it necessarily makes for a better shot.
having the subject of an image off center is a common practice in photography and design. it makes for a more dynamic shot - evokes more emotion, leads the eye or draws the eye in, breaks up symmetry.
http://en.wikipedia.org/wiki/Rule_of_thirds
http://www.digital-photography-school.com/rule-of-thirds