I agree with some previous answers. First Id offer to let him have the vehicle. If he refuses then he obviously intends to do harm to my person and is not just interested in the car.
From there I have two options:
1.) Drive away, gain enough speed to kill him and try to hit an immovable object.
2.) Make a run for it. I'd rather be shot in the back and stagger off to be found than shot execution style in the secluded field of his choice an become "badly decomposed" if ever found.
Niether is preferable to keeping the doors locked and a handgun with which to empty his brains onto the floorboard.
