Decreased Fuel Economy in Winter
A drop in fuel economy during winter is common, but if it's more severe than expected, possible causes include underinflated tires, a faulty thermostat causing the engine to run rich, or a malfunctioning oxygen sensor.
Diagnosis Details
Possible Causes
Underinflated tires due to cold weather, increasing rolling resistance.
Engine running rich because of a stuck-open thermostat or faulty coolant temperature sensor.
Failing oxygen sensor (O2 sensor) causing improper air-fuel mixture.
Related OBD-II Codes
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What You Should Do
Check and adjust tire pressures to the recommended cold pressure.
Inspect the engine coolant temperature gauge for proper warm-up.
If the issue persists, have the oxygen sensor and thermostat tested by a professional.
Related Repairs
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Disclaimer: This AI-generated diagnosis is for informational reference only. Always consult a qualified mechanic for an in-person inspection. AutOwner is not responsible for decisions made based on this information.
