The last shot most certainly is the best, however the car barely looks like it is moving still. Try panning mode 3 and taking shutter speed down to 60. A simple rundown on the panning modes is as such:
Panning mode 1: The camera is not moving at all, so the background will probably not be blurry, but the car will. I recommend this mode only for shots where you want to focus on the background and have the car completely blurred out.
Panning mode 2: The camera is moving, but at about half the speed of the car. Panning mode 2 is useful when focusing on two cars, and for having a background with little blur. This mode is also good for realistic shots that sit off of the road, like this for example.
Panning mode 3: The camera moves at the same speed as the car, this is the most commonly used panning mode, and it is used for shots that sit on the road with the car. Shots like this for example.
These probably aren't good examples, but it may help.