You see, while working you choose a light setting, in this case 'sun' with an amount of strenght and dispertion. (And a faint 'area' light in the garage)
I used a background picture with the light coming from the left side and quite high.
I adjusted the position, strenght and dispersion of my 'sun' and hit the render button...Blender does the rest.
I rendered in 1000 cycles while a render preview is 32 cycles.
So what you see in the preview render isn't always what you get when fully rendered...