Pontiac Repair: 97 grand prix, fuel level sensor, gas gauge

Question
The gas gauge on my 97 grand prix doesnt work. It reads a full tank all the time do you have any ideas for what could cause this to happen? Also do you have any idea on how many miles per gallon I should be getting hiway/in town mixed? Thanks

Answer
Hey "K"

The fuel level sensor in the gas tank is bad causing the gauge to read full al the time. As for the MPG it all depends on a lot of things type of fuel used/Octane,your driving habits,ambinet temp driving Eg a lot of cold starts I would say mixed loop driving maybe 19-21 Mpg