AudiA4A4

Hi Guys, Ive recently bought a A4 2.0t convertible 2006 s line and noticed its more thirsty than i thought it would be. Its averaging about 17mpg around town i know these cars arnt the most fuel efficient but just wondered if this is normal or maybe there might be an issue with the car? I'm driving it pretty lightly to get the 17mpg when i do put my foot down its more like 12-13mpg? I havent noticed any petrol rings on my driveway. Any help would be much appreciated Thanks in advance