Sounds low MPG...look into the three main controllers for that engine..first the O2 sensor that test the exhaust for over rich condition...(flase reading) then the temp sensor for the computer, not the one for the guage inside, this is usually a two lead device near the thermostat, if in error it may be reporting the enigne is still cold and thus the over rich condition. And lastly the MAP sensor that guages the air density in the manifold and regulates the fuel ratio that mixes with that. All these should be a quick test at the local Auto Zone/Advance Auto with the diagnostic tool. These would be the first places I would look for gas robbing.