A program car is usually only defined as such when it has low mileage, typically less than 10.000 miles. Rental cars are very often sold after one or two uses in order to be sold as program cars and also in order to replace the rentals with newer model cars to attract more customers.isadvantages. A major disadvantage to purchasing a program car is that often care is not given to the vehicle because the person using the car is aware that they will be selling the vehicle later as a program car ad not keeping the car. This tends to lead to mistreatment and improper maintenance of a vehicle.