As with what other people have said, the shader needs some work, have you got a sampler info node on there for the fresnell?

The wheels look a bit simplistic and could do with a more detials, bolt holes, bit of beveling etc, some tread on the tyres.

The top corners of the windscreen look a bit "rounded" not too sure if thats what the actual car looks like bit just seems a bit odd.

Also shouldent there be something to sepperate the fornt windows from the back?