Helping you get better gas mileage, save money on fuel, find more efficient cars, and be kinder to the environment.

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Updated Automatically on January 6th, 2009
better gas mileage

What simple, often-overlooked maintenance check can improve your gas mileage up to 3% and be critical to your driving safety? You’ve probably heard about tire pressure so often that you ignore it, but there’s more to it than you may think.

Your car’s tires can’t hold the car up by themselves. They’re not that strong. You can collapse the sidewalls of a tire by standing on them, and you weigh a lot less than your car does. The real job of supporting the weight of your car is done by the pressurized air in the tires.

If your tires are underinflated (i.e. the air pressure is too low) then you could be losing up to 3% of your gas mileage. Even worse, underinflation is the largest cause of tire failure, so your safety could also be at risk if your tire pressure is too low. Underinflated tires also tend to wear out faster and they can cause your car to handle poorly.

Even if your tires maintain their air pressure, you need to check that pressure regularly. Changes in the outdoor temperature can cause your tire pressure to change. A 10 degree Fahrenheit change in the outdoor temperature will cause your tire pressure to change by about one pound per square inch. As the thermometer drops in the fall and early winter, your tire pressure drops along with it and your tires will soon be below optimal pressure.

Get a good tire pressure gauge and check your tire pressure at least monthly. Check them when the tires are cold, not after you’ve driven the car for a long distance. The correct pressure for your tires should be in your owner’s manual. If you don’t find it there, open the driver’s door and look for a sticker on the door jamb or on the back metal panel of the door. If you can’t find the correct tire pressure, ask your car dealer. Don’t go by the pressures listed on the tire sidewall — those are usually average safe ratings for the tires and may not be optimum for your car. You may find that the recommended pressures for your front and rear tires are different. Make sure that all four tires are properly inflated for best gas mileage and safety.

Remember to check your tire pressure with an accurate tire gauge at least monthly. Overinflation can also be a problem because it can make your tires wear quickly and unevenly and it may make your car handle poorly. Keep your tires at the pressures your car’s manufacturer recommends for best tire life and gas mileage.

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Updated Automatically on January 6th, 2009
better gas mileage

One Response to “The Easiest Way To Get Up To 3% Better Gas Mileage”

    Another good tip is to replace the oxygen sensor as part of regular maintenance.

    The oxygen sensor is important to both gas mileage and emissions. The oxygen sensor (if your car has one, it most likely has at least one) is part of the emissions control system and sends important information about how the engine is running to the computer that controls the amount of fuel it gets. The sensor reads the amount of oxygen in the exhaust, converts the reading into a signal, and sends that signal to the computer. If there is too much or too little oxygen in the exhaust, the computer will detect an incorrect air / fuel mixture and adjust the amount of fuel entering the engine. The oxygen sensor tells the computer how the engine is running under all sorts of changing conditions, such as the altitude, the temperature of the air, the temperature of the engine, the barometric pressure, the load on the engine, etc.

    If the oxygen sensor fails, the computer will run the engine in “open loop.” This gives the engine too much fuel, which is safer than a lean mixture, but gas mileage suffers. The oxygen sensor is actually designed to do just that. As contaminants from normal combustion and oil ash accumulate on the sensor, it cannot respond as quickly to changes in air / fuel mixture, so it ends up giving the computer a false lean signal. For that reason a clogged oxygen sensor will cause the vehicle to use more fuel and should therefore be replaced as part of a regular maintenance plan.

    You can consult your vehicle’s owner’s manual for information on when you should replace your oxygen sensor, but general guidelines say:

    1976 to early 1990s vehicles, every 30,000 - 50,000 miles

    mid-1980s to mid-1990s vehicles, every 60,000 miles

    mid-1990s and newer vehicles, every 100,000 miles

    Since oxygen sensors are so important to better gas mileage, they should be replaced when in doubt. Other things can cause an oxygen sensor to fail, such as leaded fuel, excessive oil consumption (the condition of your spark plugs can alert you to this), road salt, oil, and dirt.

    Still not convinced? A failed oxygen sensor can also cause big dollar problems. Since a failed / failing sensor will make the engine use more fuel, it will also cause more unburned hydrocarbons to enter the exhaust. This will cause the catalytic converter to run hotter than normal, and if it runs hot enough, it will melt internally forming a partial or complete blockage. This could cause the engine to stall and suffer a drastic performance loss due to increased backpressure in the exhaust. Not only will this reduce gas mileage, it will increase emissions, most likely causing your car to fail inspection. Replacing a catalytic converter is expensive, as much as $1,000 on some cars.

    Periodically replacing the oxygen sensor can increase gas mileage as much as 10%-15%.

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