Mitsubishi: 2003 Diamante-Erratic Fuel Gauge

Our 2003 Diamante has developed a strange problem. I filled the tank up
the other day and drove for about 120 miles. My wife was driving the
car yesterday and said that she had to stop to get gas as it was on
empty. She said it only took about $14 to fill it up. I immediately got
into the car and it already said that half a tank was gone....any
ideas???

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Without getting out the service manual and checking I want to say that
your system may not use a float. I think there is a sensor on the fuel
pump for the gauge. I suspect it has become fouled by some additive in
the gas. I have had this happen twice and a can of Techron from the
Walmart seems to fix it every time. I could be wrong though....?