Ok the best way to learn is through critique so here goes:
1. You clipped the blacks. There's no detail at all below the car. The vignette does not work as it just makes everything too dark. The car is "leaning" to the right a bit, and the crop is too tight. It's slightly off center.
2. Better exposure than 1, but still no detail in the wheels or in the grass under the car. It's blown out on the horizontal surfaces. Crop is too close and it cuts off the front of the car in a weird place.
3. Car is leaning to the left as well as slightly turned to the left. Again, you have the issue of losing shadow detail and part of the hood being blown out. The roof is cut off, and the heavy vignette doesn't work again.
On all of them: Too much sharpening and the white balance is off.
Things you can do to change: Don't get so close to the car. Take photos that are level and straight and give the car room to breathe in the frame. Try different angles by holding the camera above your head or crouching down. Go lighter on the editing, especially the vignettes and sharpening. The hood/door lines should not be jagged. They should be one smooth line. The jaggedness is caused by over-sharpening. The light is pretty crappy in this as well. Early afternoon is probably the worst time of day to be taking photos as the camera does not have as large of a range that it can expose correctly as we do. Light around sunset/sunrise is always more camera friendly. You can deal with harsh sunlight by having flash or reflectors to fill in the shadows.
Just some things to consider and help you out next time you take photos.