Piteu

Hi there, I purchased a 2013A5 DIESEL SPORTBACK 2.0 TDIe 136 SE 5dr this week, my surprise is that I have done 4*40 miles motorway trips and I get max 45 mpg. Audi claims 72.4 mpg. I understand this is a theoretical value but 45 mpg!!! I am not a fast driver at all and I am used to get over 50 mpg with no issues in other cars. What could be the reason of this low mpg? Thanks for your help