Technically black on black... Mostly everyone tried to do something low key and I think using a low key shot could have helped create the illusion of being a real car. Try adjusting levels to drown out the texture on the black background and making it darker.
Nice idea. Could have been improved by putting the car on a stand, and having the cloth be a blurred (or invisible) background. Also, the reflections on the hood are very distracting.
Some of my opinion:
1. The background is not black enough.
2. The car is not clean enough.
3. There are some distracting reflection on the car. Maybe you could improve it by keeping the environment as dark as possible and using some modifier to control the light.