having to put gas in vehicle every 2-3 days

I mentioned this problem 2 weeks after getting the car. I took it back to VW to get a check up and I mentioned it to Paolo the service advisor. He tried to show me on the dash on how to monitor how much gas usage I use. I still didn't understand. So I left. After several months of this I got in contact with VW corporate to see if I would have to pay out of pocket to have the car diagnosed. They told me no it would not and I could take it to any VW dealership in the area. This problem continued on. So finally took it in on Sept 2015. They examined it and said everything came back diagnostically correct. I took it back again on Oct 2015 again nothing found. Took it back again at the suggestion of VW Corporate on Dec 2015 and this time they told me it was my floor mats that was causing the problem of the gas consumption. Seriously. These are the same mats I have had since purchasing the car. Why didn't the other technicians find it?