As the car hire facility is outside the airport campus you will need a little bit more time than if it was right beside the terminal building. The shuttle bus is very regular but it can take time in heavy traffic so you need to prepare for that. The return process shouldn’t take more than 20min from the time of parking in the rental facility but do allow for delays at peak times. Allow yourself at least an hour on top of your normal pre-departure time to return your keys and documents, wait for the shuttle and to get back to the terminal. There are taxis available at the facility too if you are short on time. Search car hire on KAYAK