The Fiat is taking off… Many problems here:
- Lighting mismatch: the red car is lit from slightly back, slightly right while the fiat is lit from slightly front, slightly left.
- Color mismatch: likely very hard to fix because the target picture has been heavily processed (so it"s not just a color temperature problem, probably also a brightness/contrast or even HDR one)
- Perspective mismatch: the red car is shot slightly from above with a camera pointing slightly down, when the Fiat has been shot at hood’s height, with a camera shooting horizontally.
- The Fiat wheels have no shadow. If you want something to look settled on the ground it has to have a little shadow where it touches the ground. That one is not that hard to fake…
- The ground under the Fiat looks lit from an electric heater under the car. Again, not hard to darken the whole thing significantly (see the other car).
As a rule, the chances that you can transplant a random picture into another random picture are very small, and many examples you see on the web use very carefully selected images or even images taken for that purpose.
A counter example is bunch of group pictures I took recently. No picture where everyone was looking at the camera with an acceptable smile, but since all the pictures where taken in a few minutes, lighting and perspective was the same on all and it was very easy transplant heads to make a group picture with everyone looking good.