During a road trip, the gas light on Justin Davis' car went on and he pondered the question that has puzzled mankind since the invention of the automobile: just how far can you drive after the gas light comes on?
The "Tank on Empty" concept is simple: Your light comes on, you hit the trip meter, drive for as long as you can -- or dare -- and then go to the site to submit the number of miles you travelled beyond E. For example, 129 drivers have entered data for the Toyota Corolla, which I drive, logging an average of 44 miles after the light.
Davis continues: "The feedback I receive usually identifies three types of people: The ones who think it's a fun idea (my favorite); people who don't think the information is detailed enough because it doesn't take into account engine size or number of passengers or something (the pedants); and, the people who have to warn against driving on low gas because it'll hurt your car or could kill you or something (the overreactors). It's fun to categorize them as people leave messages."
Link: Davis' website Tank on Empty | Article on Network World by Paul McNamara
Running on empty will only damage an in-tank fuel pump and only if you make a habit of it. Cheap cars like Volkswagens and Willys and Crosleys used to lack fuel gauges entirely, instead they had a reserve tank that held about half a gallon. You'd let the thing run dry, switch to the reserve tank, and go find a filling station.
We once got the Toyota minivan to go a mile (with turns and stops) with only pushing the gas pedal for about 5 seconds in the beginning. (Probably could've done more, but we were at the end of our trip...)
The varied auto manuafacturers all have their own idea of the optimum "empty reserve" (an actual automotive engineering term) for their particular customers. Personally, I'd like a tank gauge to read right on F when it is full and right on E just before it sputters and dies, with accurate linear reading in between. Unfortunately, the greater public is frankly rather dim and are easily fooled into thinking the car gets better fuel economy if it takes *forver* to move off "F" and then takes 100 miles to finally die after E has reached. As a result, automotive engineers deliberately calibrate the pump sender units to read high when fuel, low when empty, and varying slope in between. All cars do this, but the more a car exhibits such goofy inaccurate behaviour, the dumber the automaker thinks its customers are. Like I said, all cars are different, but no automaker delivers truly accurate gauges. If your model goes forever on E, they think idiots are the primary buyers.
@sid - nice response