I'd like to rent a car at midnight as my flight gets in on the 27th at 23.10, is this possible at Gardermoen Airport?
Although the suppliers at Oslo Gardermoen Airport advertise that they close at 23:30, they will remain open providing you have entered your flight number on this website.
There will be a “Late hours fee" (approx. €70).
Can I return the rental car at 04:30?
Yes, you can use the key drop box facility.