Nice lawnmower (a Dean comment).
Take the car to a decent location. Fields don't work for cars.
Are the shots HDR'd? They don't have enough contrast.
Try the car on an overcast day with no direct sunlight, choose a location like a brick warehouse car park, green fields dont look right, you can also use a race track if you are near one.
HDR is good for cars but better if they have lighter colours than black.