the high pressure fuel pumps in modern cars produce heat and need to be cooled. many are located in the fuel tank so that they are cooled by the residual fuel. running too low on fuel is not cool, pun intended. repeatedly running low or possibly out of fuel will shorten the life of the fuel pump. that's one reason it is often recommended to fill up when you get down to 1/4 tank. the good news is that car manufacturers often slightly understate the actual size of the fuel tanks in their vehicles. so if it takes 15 gallons of fuel to fill your crossfire there was probably somewhere between 1-2 gallons already in there to help prevent damage to the pump.