Police said the 30-year-old man walked into a car dealership in the southern city of Melbourne last Friday and asked to take a 2008 model Honda Accord for a spin.
After chatting with a salesman for 20 minutes and convincing him he was a genuine buyer, the man filled out the necessary paperwork then took off in the car before the salesman could get in the passenger seat.
He turned up on Wednesday, about 3< 700km away near the Northern Territory town of Tennant Creek, where police picked him up after he drove away from a garage without paying for fuel.
Officers checked the licence plates, and found toiletries and a toothbrush in the car.
Car dealer Ian McKenzie said the driver put 6< 200km on the clock during his try-out.
"He's got to have been in the car nearly all day, every day," he told Melbourne's Herald Sun newspaper.