I've been getting between 270 and 300 miles per tank on my 2007v6 limited. I am running a OME/Superflex lift and 285/75R16 BFG ATs. Does this sound right?
Is that mileage you listed from the odometer or actual miles. With bigger tires (yours are about 34 and a half inches tall - 614 revolutions per mile), you will be traveling farther than the odometer lists (stock tires are about 31 and a half inches tall - 660 revolutions per mile).
I have stock tires with a V8 so my mileage can not really be compared to yours but I can get 390 per tank. The 390 was calculated if I run the tank dry. I get 17.1 MPG overall average.