Hmmm...My truck gets 11.7 MPG, and my P5 averages 23.8.
Unless you're REALLY dogging on it, 24mpg seems awfully low. In the summertime with the AC running any time the car is, i average about 30. In the winter time when i don't use the AC (for both months) I usually average 34-35mpg. Glad it's running good for you but unless you're driving it like you stole it, something still seems off to me.