On most vehicles, the fuel pump is located inside the fuel tank. Gasoline in the tank helps keep the fuel pump cool. When there’s too little gas, the fuel pump can overheat, causing it to wear out faster. So, you need enough fuel in the tank to keep the pump submerged.
Sediment is another concern when you’re driving on empty (or close to it). The sediment and contaminants that sit in the bottom of your gas tank can be pulled into the fuel pump when the fuel level is low. These contaminants can clog and stress the pump if they build up significantly. This is possible—though less likely—even in modern fuel pumps equipped with adequate protective screens or filters.
Replacing a fuel pump costs a lot more than a tank of gas: $500 or more in parts and labor, depending on your car.