I recently bought 2007 Chevy Tahoe LTZ and made already about 700 miles - mostly in the city. I started with really bad MPG rating and slowly it's been going up to where it's now - 11.7 MPG. I love my truck but I'm kind of disappointed with that rating which is not even close to sticker rating - 15/16 MPG city. I just kind of wonder if anybody else got the same rating or maybe there is something wrong with my car???? Or maybe it will still go up??? I'm running this car on Mobile gas - 87 octanes and drive it normally (not too fast, not too slow).