Is it bad to drive on a low gas tank?

The traditional warnings were that a low tank lets the in-tank fuel pump run hot without surrounding fuel to cool it, and that the pump draws sediment from the bottom of the tank into the fuel filter. Both had some basis in older vehicles, but modern fuel systems weaken the argument considerably: contemporary tanks are cleaner, plastic rather than corroding steel, fuel is filtered before and after the pump, and pump designs and reservoir baffles keep the pickup submerged even at low levels. There is little evidence that habitually running to a quarter tank meaningfully shortens pump life in a current vehicle.

Where the caution retains force is at genuinely empty. Running completely out of fuel can leave the pump running dry, which is harder on it than low fuel, and on diesels it introduces air into the fuel system, which on many engines requires bleeding before it will restart. The stronger everyday argument is simply practical: fuel gauges are approximations, the low-fuel warning provides less range than people assume, and running out places you on a shoulder in traffic, which is a real safety exposure. Filling at a quarter tank costs nothing and removes the risk. In deep cold, keeping the tank fuller also limits condensation and gives you a heat source if you get stranded, which is a genuine winter safety practice in northern climates.