How far can I drive after the low fuel light comes on?

Typically 30 to 50 miles, but the honest answer is that it varies enough between models that treating it as a reliable reserve is a mistake.

The light is triggered when the level in the tank falls below a set point, and manufacturers choose different reserves. Small hatchbacks often hold around five to seven litres at that point; larger vehicles sometimes ten or more. Combined with differing fuel consumption, the real-world range after the warning can be anywhere from about 25 miles to over 80. Many cars display a distance-to-empty figure, and that estimate is calculated from recent consumption — so a motorway average shown as you enter stop-start city traffic will overstate what remains.

The gauge itself is not linear, which surprises people. A float arm in an irregularly shaped tank does not move proportionally to volume, so the needle often falls slowly through the upper half and quickly through the lower.

There are reasons not to make a habit of running low beyond the obvious. In older vehicles the fuel pump sits in the tank and is cooled and lubricated by the fuel surrounding it; running consistently low raises its operating temperature. Sediment settles at the bottom of a tank over years and is more likely to reach the filter when the level is low. And on steep gradients or hard cornering, fuel sloshes away from the pump pickup and the engine can cut out with fuel still in the tank.

Modern direct-injection systems are also expensive to repair if run completely dry, and diesels in particular may need bleeding after running out.

Treat the light as "fill up at the next station", not as a countdown.