it could be your fuel pump..or you gauge could be bad and when it shows and eight of a tank its really empty..but im sure your fuel tank doesnt hold more then 10 gallons...you shouldn't run your car on a quarter or less cuz that fuel pump is really have to work to draw that fuel and that causes your pump to over heat and thats the cause for fuel pumps going out..so your fuel pump is probably going out.. just try and keep it half or better..hope this helps