Positional potential energy is the energy that an object has because of its position relative to a force field. In the case of a car, the force field is gravity. The higher the car is, the more potential energy it has.
Internal energy is the sum of the kinetic energy of the molecules that make up the car, plus the potential energy stored in the chemical bonds between the molecules. The faster the car is moving, the more kinetic energy it has. The more energy that is stored in the chemical bonds, the more potential energy the car has.
The total potential energy of a car is the sum of its positional potential energy and its internal energy.
