It seems like my fuel is being used too fast. When I have the display on how many miles I have left on the fuel tank, it goes down 4 or 5 miles everytime I accelerate. However it usually goes back up 3 or 4 when I brake. What could this be?

 

The float in the tank goes up and down as fuel shifts in the tank. You're just watching too closely.

 

This could be a first indication of failure of the fuel tank sending unit.

 

Indications other than steady state cruising are nothing more than vague estimates based on crude calculations during transient state. Ignore them.