Poor Fuel Economy

Definition: Fuel economy, as measured by an actual road test, is noticeably lower than expected. Also, economy is noticeably lower than it was on this car at one time, as previously shown by an actual road test.
POSSIBLE CAUSE ACTION
Dirty air filter Clean or replace

Fuel metering Check air/fuel ratio, (02 sensor voltage)
Perform injector service (cleaning), Fuel Injector Cleaning Procedure
Check fuel pressure (check vacuum line and return hose), Testing and Inspection

Speedometer inaccurate Check speedometer calibration