As others have said, the range on the readout is just an estimate, which is continual, so for example if you start going uphill, or press on, it drops almost immediately. I tend to fill up when the range drops below 100 miles, but that's just me. There is something satisfying in getting a good range out of one tank, but you have to weigh that against the probability of running out of fuel - and dragging the bits of silt and whatnot that accumulate at the bottom of fuel tanks over time into the fuel pump. In general, I drive to the green eco light, and I'm averaging over 50mpg, so I don't fill up that often. Fantastic!