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Q: Low gas mileage

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The car used to get EPA mileage (21/31/25) but now it gets 22 in the summer and as low as 15 in the winter, depending on the outside temperature. These figures are for mixed driving. The car has had this problem for over two years.

I have taken it to a dealer and a garage and neither can find the problem because it's not producing any diagnostic code or a light on the dash. I have had the air filter and the spark plugs changed but neither has affected the mileage.

Thank you.

My car has 55000 miles.
My car has an automatic transmission.

Hi there. Depending on where you live, the difference in summer and winter fuel mileage might be related to the type of fuel being used. In cold weather climates, it’s common for fuel stations to switch to a "winter blend", which is a less refined, but oxygen-rich fuel that is made for running in cold conditions. On the average, fuel mileage can be 20% worse in winter than summer in general. However, this doesn’t explain the main drop you’ve experienced in recent years. In general, dirty mass air flow sensors, fuel injectors and the throttle body tend to cause this issue. You might want to have a professional mobile mechanic come to your location and complete a car is getting worse fuel mileage inspection.

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