The Philmobile is an automobile that was invented by Philip in Ni no Kuni: Wrath of the White Witch.
In the post game after completing errands for the Conductor, he will allow Oliver to relive his old dream, driving the Philmobile and hands over the Philmobile key to Oliver. With the Philmobile key Oliver can travel using the Philmobile that was seen during the beginning of the game.
In The Tale of a Timeless Tome, The Conductor would reclaim the Philmobile.