Magic wand the car, or magnetic laso the car
If you want good clean selections always use the Pen tool!! OP I sorta did the same thing you were going for while I was making a background for my desktop. All I used was the pen tool, quick masking, and gradient tool. Took about an hour all said and done.
Original picture:
Final:
I accidentally masked out part of the front tire because the monitor I was working on is too dark and didn't notice it until I looked at it on another computer.:lol: