Diagnose Sudden Fuel Economy Drops in Vehicles

Cost Savings

Checklist Tasks

• Review fuel receipts and odometer logs for calculation errors.
• Check tire pressure with a calibrated gauge for underinflation.
• Inspect air filter for clogging or dirt restricting airflow.
• Scan for engine codes with an OBD-II reader for sensor faults.
• Examine spark plugs for fouling or wear affecting combustion.
• Test for dragging brakes by spinning each wheel for resistance.
• Verify oil change history and correct viscosity.
• Check for exhaust leaks near oxygen sensor disrupting fuel trim.
• Inspect roof racks or accessories that may increase drag.
• Review recent driving patterns for excess idling or aggressive driving.
• Examine fuel cap seal for cracks or poor fit causing vapor leaks.
• Monitor engine temperature gauge for slow warm-up or overcooling.