Best Gas Mileage – Replace Oxygen Sensors

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 best 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%.

Reference Links:
1) Purchase new Oxygen Sensors at Theautopartsshop
2) For more information Please check this link