Poor Fuel Mileage

If fuel economy is lower than expected during a road test, or has changed from previous road tests, check the following items:

• Check thermostat operation and heat range.
• Ensure coolant level is okay.
• Ensure tire pressure is correct. Check for the following vehicle operation conditions: A/C always on, vehicle heavily loaded, or constant heavy acceleration.
• Perform diagnostic circuit check. See TESTS W/CODES article in this section.
• Check air cleaner condition.
• Check speedometer calibration.
• Perform a visual inspection of all vacuum hoses and ignition wires.
• Ensure ignition timing is correct.
• Ensure fuel pressure is correct.
• Check spark plugs for wear or damage.
• Ensure engine compression is correct.
• Ensure torque converter clutch operation is correct. Refer to article SYSTEM/COMPONENT TESTS in this section.
• Check brakes for dragging.
• Recheck fuel mileage.