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There can be many reasons why your vehicle burns more fuel than usual. The issue can be as simple as your driving habits or changes in weather. Spark plug issues and dirty sensors may also negatively affect your vehicle’s fuel economy.

11 Common Causes of Poor Fuel Economy

Are you taking more trips to the pump than usual? Here are possible reasons why your vehicle consumes more gas than average.

Dirty Oxygen Sensors

Oxygen sensors measure the amount of oxygen in the exhaust. These sensors help your ride’s computer correct the air-to-fuel ratio in your engine.

If your oxygen sensors are dirty, they can give incorrect measurements. This can trigger your fuel injectors to deliver more fuel to the engine than what’s needed.

Spark Plug Issues

Issues with your spark plugs can cause engine misfires. If your vehicle doesn’t get the right amount of spark it needs for the combustion process, your engine won’t start. Thus, fuel and engine power are wasted.

spark plug cause of engine misfires
Issues with your spark plugs can cause engine misfires.

The same problem can happen to other parts of your ignition system like your coils and wires.

Dirty Mass Airflow Sensor

Your mass airflow sensor measures the amount of air that flows through your engine. Similar to oxygen sensors, the information it collects helps in calculating the proper air-to-fuel ratio in the engine.

A dirty mass airflow sensor might not be able to measure airflow accurately. This can affect the amount of fuel that’s injected into the engine. Aside from poor fuel economy, you might also notice frequent stalling.

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Some prefer to clean this sensor with a cleaning spray. Note, however, that cleaning a MAF sensor is not a good idea. The windings on the electrical portion of the sensor where the air passes through can be so small, so the cleaner won’t be able to clean it. It might work for a little while, but you’ll still have issues with it in the future.

Note, however, that cleaning a MAF sensor is not a good idea. The windings on the electrical portion of the sensor where the air passes through can be so small, so the cleaner won’t be able to clean it.

Anthony Harlin, ASE Certified Master Automobile Technician

Low Tire Pressure

Underinflated tires can cause increased rolling resistance.

Modern vehicles are equipped with a Tire Pressure Monitoring System (TPMS). However, most TPMS will notify you only when there’s a significant or rapid change in the pressure of your tires—when your tires are 25 percent below the manufacturer’s recommended PSI.

You can check your tire pressure manually by following our Tire Inspection Guide.

Clogged Engine Air Filter

A dirty air filter can restrict airflow, so there’ll be less oxygen in the fuel mixture. Once this happens, your engine will consume more fuel than required. This is common for older vehicles that can’t detect poor air quality.

To prevent this from happening, make sure to check your owner’s manual for the recommended air filter replacement or cleaning interval.

Skipped Oil Change Schedule

Routine oil change improves engine performance and helps maintain good gas mileage. That’s because clean oil promotes proper lubrication of your engine components. It keeps your engine running smoothly.

Old and unchanged oil can thicken in time. Thick oil won’t flow smoothly through your engine. Your engine will have to work harder, resulting in added fuel consumption.

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Fuel Injector Issues

Your fuel injectors supply fuel to the engine. The spray pattern of these injectors must be precise. Once these injectors get clogged or dirty, they might not be able to spray fuel efficiently when needed.

If your vehicle suffers from fuel injector issues, you might have to clean the injectors or replace them.

Worn Piston Rings

Your piston rings serve as a seal between your vehicle’s piston and cylinder wall. Once the seal is broken, your engine will lose pressure and suffer from poor fuel efficiency. This issue is more common in direct-injected vehicles.

Driving Habits

You can also consume more fuel if you’re often speeding up or accelerating. In fact, according to, a vehicle’s fuel efficiency decreases at 50 mph. To conserve fuel, make sure to stick to the speed limit.

Too Much Use of A/C

You consume fuel when you turn on your vehicle’s air conditioning. According to existing data, blasting your A/C often can reduce your car’s fuel efficiency by 20 to 50 percent.

If you want to conserve fuel, you can look for other ways to cool down your ride’s cabin. For instance, you can park your vehicle in a shaded area. Depending on where you’re driving, you might also want to drive with the windows down.

Cold Temperature

Low temperatures can increase engine and transmission friction. It’ll also take your vehicle more time to warm up during winter. Your fuel consumption can increase during cold months. Your car’s heated seats and defrosters can also consume fuel.

Thermostat That’s Stuck Open

Your fuel economy will also decrease because of an issue with your thermostat. That’s because your engine won’t warm up as it should once your thermostat is stuck open. Make sure to watch out for symptoms of a failing thermostat.

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What Is Good Gas Mileage?

car refuel after traveling
Good gas mileage means that your vehicle is consuming less gas at a larger distance.

Good gas mileage means that your vehicle is consuming less gas at a larger distance. Gas mileage is usually measured in (miles per gallon). Experts say 23 MPG is considered good gas mileage. However, it’ll depend on many factors like your ride’s exact year, make, and model. You can read our article about gas mileage to learn more about it.

Hybrid Options

If you’d like to save more money on gas, you can invest in hybrid vehicles. These vehicles still have a combustion engine, but they also have an electric motor that operates when traveling at low speeds. However, it’s important to note that these vehicles are priced higher on the market, so you’ll have to shell out a large sum of money to buy them. Although they’re expensive, the benefits in fuel costs afterward will surely be worth it.

Whether you own a hybrid car or a purely fuel-powered vehicle, it’ll help you save up on gas if you’re aware of the possible issues that can cause your ride to consume more fuel. Have these problems right away, so you can have more savings and avoid any hassle while you’re driving.

About The Authors
Anthony Harlin, ASE Certified Master Automobile Technician
Reviewed By Anthony Harlin, ASE Certified Master Automobile Technician

Technical Reviewer at

Tony Harlin is a Master Gas and Diesel Diagnostic Technician with over 18 years of experience. He works full-time at a large independent automotive shop as a driveability and repair technician working on all types of vehicles with a focus on diesels. ASE certifications include A1-A9, L1 and L2, as well as X1.

CarParts Research Team
Written By Research Team

Automotive and Tech Writers

The Research Team is composed of experienced automotive and tech writers working with (ASE)-certified automobile technicians and automotive journalists to bring up-to-date, helpful information to car owners in the US. Guided by's thorough editorial process, our team strives to produce guides and resources DIYers and casual car owners can trust.

Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.

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