mrasuring a fuel level of small Generator

Hi everyone ,i want to measure fuel level of small generator through arudino and Gsm Interface Please tell me if any one know how to i measure fuel level ?? and what kind of sensor i use for this ?? :(

A motorcycle tank fuel gauge based on a home-made capacitance sensor was discussed recently http://forum.arduino.cc/index.php?topic=194373.0

It seemed to be a safe design.