Take it back. I had the same thing with my wife's X5. It kept getting worse and worse.
In the worst case scenario you will ignore it, then over fill it, and pump gas down the ventalation tube and ruin the charcoal canister... have a gas smell for days... get it serviced 4 times, barely have an answwer and then just have to start replacing costly parts until you get lucky.....not that I know abut that....
2009 328i Sedan | Titanium Silver | Black Dakota Leather | Aluminum Trim | Sports | Premium | Cold Weather | Paddle Shifters | 35% Tint | Polarized Lense |... and Lots of Pride
2001 X5 3.0 | Titanium Silver | Grey Dakota Leather | Premium | Activity Package| Climate Package | >200,000 miles |... and lots of repairs!