Uhm, well, actually the more you stay away zooming on the car, the less "deep" the focusing will go behind it. No idea exactly why technically, but it's like that. Of course by blocking your F to the max you will slightly avoid it, but well, it's cool sometime to have a very blurry background. That said, when you pick a nice scenic location, you don't want to really frame very tight around the car.
And no, you can't shoot while zooming, you need a special lense to do so
Again, this week try to take pics standing close to a car and then step some meters away and do the same after having zoomed in, you will see what we mean