The maximum amount of mileage customers can reach depends on the rental agreement. More affordable plans typically incorporate a lower amount of mileage. Flexible mileage plans are available from some providers, as are high mileage plans. In the event that a customer goes over the allocated mileage, the additional cost is added on to the agreement and will be due upon return of the vehicle. Renters are responsible for keeping the fuel tank topped up with fuel throughout the agreement.