Corrected entry: In the scene where Greg is getting acquainted with Pam's parents, Jack asks him what kind of car he's driving, and Greg tells him it's a Taurus. However, minutes before, as they drove in, you could see the back of the car and it was clearly a Ford Contour, not a Taurus.
Correction: Greg may not know much about cars. He could have not been paying much attention to the make and model of the car (evident since he didn't even pick the colour) when it was rented.
Correction: Actually he is driving a Ford Taurus. While Greg doesn't know that much about cars, from someone that does, there is a clear difference between the Taurus and the Contour.