Mileage Headed Downhill? (What Causes Bad Fuel Economy?)
December 28, 2025
Name someone you know who enjoys spending a lot of money on gasoline. Yeah, me neither. That’s because it costs quite a bit to keep fueling your vehicle.
One way to save money on gas is to get good fuel economy, and most of today’s vehicles are designed to maximize your mileage. But you might find you’re filling up more frequently than you used to and are wondering what can cause your fuel economy to tumble. Here are a few possible reasons your mileage has been headed downhill.
A logical spot to start is in your fuel system. You may have a faulty fuel injector or an old fuel filter clogged with debris. Another problem might be oxygen sensors, which measure the air coming into your engine and the emissions going out. An illuminated Check Engine light may be a sign of trouble there. Plus, worn-out spark plugs can reduce your fuel economy.
Under- inflated, or over-inflated, tires can also be a cause. Make sure they’re all at the same pressure. When’s the last time you changed your engine air filter? One that’s clogged and dirty can rob you of better fuel economy. Another bandit is a dirty, leaky, or clogged exhaust system, so have it checked out by a pro.
Finally, how you drive can also mean wasted gasoline. Jackrabbit starts and speeding use more fuel than smoother acceleration. And if you often sit there with your engine idling while you’re waiting somewhere, you’re throwing fuel away. Just turn the ignition off.
Try out some of these fuel-conserving habits and they’ll pay off for you in the long-run.
Auto Lab Troy
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Troy, Michigan 48084
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