Poor Fuel Mileage

Inspect for fuel leakage.
Ensure fuel is of good quality.
Ensure fuel system pressure is correct.
Inspect for fuel leakage.
Inspect accelerator pedal linkage.
Check clutch for slipping.
Ensure emergency brake does not drag when released.
Ensure engine has sufficient compression.
Check cylinder leak down.
Ensure ignition and valve timing are correct.
Check HO2S for proper operation.
Test intake air temperature sensor operation.