The biggest thing ruining it is the lighting - your light setup gives a confused impression of the lighting such as the shadows that doesnt match with the strongest lightsource, the sun (even though its setting) and you have light on the back of the car as if another car is parked behind it - but it's not working as it should. You probably should have moved the light further away, to get a smoother falloff.
The bright white reflections upo front are simply too white - on a red car - with a yellowish sun. Doesn't match at all. Should look softer too.
also remember that you don't HAVE to cast shadow from all lights. there are 2 shadows that I could see and they just add more to the confusion.
i dont have a sunlight,and no light behind the car. there is small light above the car which if i lighten ,than car is invisible O.O its only a background pic with a fail hdr i cut out from original pic. which i tried rotate million times,but didnt work. thats why i posted fail render
It doesn't matter if there's literally a light behind the car or not. the point was that it looked like there was one - and sure, there can be one, its not like the sun is the only source of light on earth, but it added to the confusion.