Hi. I've had my 2017 Wolfsburg edition for about 5 weeks now. 55k miles to start. Dealer did a full tune-up (air filters, plugs, etc) before sale. I started out calculating my MPG just to see what I was getting. On 1st tank of gas I got 23mpg. Almost a month later, with the same driving habits and 93 octane gas, it dropped to 13.5mpg. Then I started being able to see the gas gauge needle move during an evening's driving of maybe 15 miles. Last check was 9.8mpg!! I've noticed no change in how it runs, engine seems the same. I just don't have a clue why the gas mileage would somewhat suddenly drop so drastically. Any thoughts on this besides winter gas, driving habits, etc??