yeah,i know how a capacitor works,and the tank is made of plastic,not metal.the di electric constant will change as the fuel level changes,as air will take its place,and the distance also does matter as capacitance = episilon x area/distance...so more the distance less the capacitance,so,my main question now is,will it be able to detect capacitance when the plates are seperated by 15cm or so...or should i increase the resistor value for a larger resistance?