Volvo Repair: Gas Mileage - 2005 S80 2.5T, average miles per gallon, gas mileage

Question
I recently purchased a used 2005 S80 2.5T. It looked clean, cared for and seems mechanically new. The car has 19k miles. Carfax suggests it was previously used as a rental vehicle. I notice the average miles per gallon on the computer is around 16-17 in local driving - a far cry from the 21 mpg on the sticker. Should I have it looked at by Volvo? What could be the problem(s)? Or is the 21mpg a fictitious number? Thanks for your feedback.

Answer
Mike,  I would suggest filling the car up and resetting the odometer trip 1 to zero and figure it out manually.  Since the car has 19k miles, its still under factory warranty.  I would have the dealer take a look at it.  These cars dont get great milage as it is.  Since its a turbo car, 18 is probably about right but try the manual milage theory first.  Roger