The Flying Ford Anglia only appears in Harry Potter and the Chamber of Secrets. Mr. Weasley had enchanted it to fly, become invisible and to be able to fit in eight people. It also has some intelligence which can be gauged from the fact that the car came to Harry's and Ron's rescue in the book. And we also know that the Forbidden Forest had turned the car wild and it had taken to roaming the forest.
Now keeping these things in mind, I have two questions.
What would happen if the car runs out of fuel?
Does the car actually need fuel?