The 2011 Lincoln Navigator is one of the biggest, heaviest SUVs available, so it probably doesn't come as much of a surprise that it's also one of the thirstiest. With fuel economy ratings of 13 or 14 mpg city, and 18 or 20 mpg highway, the Navigator isn't at all green.
However, much of how green the Navigator is depends on how you plan to use it; fit seven or eight in the Navigator, and it's a greener pick over taking two compact or mid-size crossovers.
All 2011 Navigator models are E85-compatible, but with that fuel its ratings drop to 9/13 (4WD).
The 2011 Lincoln Navigator drinks gasoline at alarming rates, though it's arguably not as bad if you're using its tremendous passenger capability and comfort.