[prerok]

Not that I am any sort of expert on the subject, but the way I understand it is:

1. If you have a fossil you can carbon date it based on the amount of C14, which is an isotope of carbon, and is present in relatively stable amounts in living organisms. That's because a living organism takes carbon from its environment and then incorporates it in itself and C14 is continuously generated in the environment because of the radiation from the sun. As the organism dies, the intake stops, so then you can determine its age based on the half life of the C14 and the amount of it still remaining in the remains. Long story short: it cannot be accurate.

2. You can only measure this in remains of dead organisms. Maybe in leather, if the car had some, otherwise I don't think you could easily carbon date a car :)