You're not necessarily that lucky apocrates. As mentioned, 4x2's should get slightly better mpg than 4x4's. Here's what my records show since I have owned my X. Every tank is included in these averages including 100+ weather tanks and off-road tanks. I take great care to be consistent in how I fill my tank (i.e. when the handle clicks off, I never add a smidge more). I keep all of my gas receipts that give gallon amounts to three decimals and I use the trip odometer which reads to one decimal. Excel keeps track of the rest. I usually fill up shortly after the light comes on too.

Average MPG: 15.46
Average range: 256 miles
Average Gallons added: 16.52

Very close to what Nissan claims, huh.

This also brings up something interesting. You want to know how far you can push it before filling up? Well our tanks are what, 19.4 gallons? If the light comes on when there is approximately 19.4-16.52=2.88 gallons left, and the average is 15.46 MPG, then you should have about 2.88*15.46= 44.5 miles left when the light comes on. Let’s round it down to 35 to be safe though.