It might be worth having a look in the Mk V and Diesel sub forums here for more examples of real world economy. Yours does sound like it might a bit thirstier than average.
Maybe if you can give us some more info about your load, tyre size & pressures, cruising speed, driving style, roof racks/top boxes etc we can comment more usefully.
The economy calculated by the trip computer can sometimes be inaccurate (usually a bit optimistic). The best way to get accurate fuel consumption figures is to use the fill to fill (or brim to brim) method, recording distance and actual fuel put in, prfereably over at least 2 or 3 fills.
Note also that the long term average and totals in the trip computer [memory (2) ] is reset every 99.9 hours of driving.
My 2.0 TFSI gets more like 9-11 l/100km, but it is a petrol and I do lots of short trips and tend to drive a bit enthusiastically (when you do less than 7,500km a year in a car fuel costs aren't usually much of a worry).
2017 MY18 Golf R 7.5 Wolfsburg wagon (boring white) delivered 21 Sep 2017, 2008 Octavia vRS wagon 2.0 TFSI 6M (bright yellow), 2006 T5 Transporter van 2.5 TDI 6M (gone but not forgotten).
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