My Yellow 427 Cobra from PD Cup runs takes top honors with exactly 1,000.0 miles, while the GT-One Racer has 990.8. I have 10 other cars that have elipsed the 600-700 mile mark. Total garage mileage is somewhere in the 27,000's.
My CLK Touring car that I won from the Mercedes series has a LOT of miles on it. I went a long ways in the game with that car unlocking car after car with it. I think it was in the Ameture series but not positive.