Location and lighting.
Shot early in the morning, or late in the evening. Mid day with bright sun is a difficult shoot. Mid day with complete cloud cover is nearly ideal. Kind of like shooting in a studio.
Try different lenses, focal lengths, and distances from the car. If you find a structure you want to use for a back drop, park the car a good distance away from it. Usually don't want to be right up on it.
Keep that horizon level, especially on straight on front or rear shots. Get as centered as you can and level the horizon. Check the difference this one simple adjustment makes. ....Well that and a bit of color adjustment.
