Changing Your Cars Engine Air Filter

AAA Auto Repair Article
By AAA Automotive
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Do you replace your car’s engine air filter too often? For years, service technicians and the Environmental Protection Agency encouraged motorists to change the engine air filter frequently to ensure maximum fuel economy. While that advice was sound for carbureted cars, a U.S. Department of Energy study found that air filter condition has no significant impact on the fuel economy of modern fuel-injected engines, although a badly restricted air filter will reduce the engine’s maximum power output.

(AAA image)
Today, most automakers recommend that the engine air filter be inspected regularly, but replaced only as needed or at extended mileage intervals. More frequent replacement wastes money without providing any real benefit. In a relatively clean city or suburban driving environment, an air filter may be good for 20,000 miles or more between changes. However, driving in dusty rural conditions can result in the need for a new engine air filter at more frequent intervals.


Identifying A Dirty Filter

How do you know when your engine air filter needs to be replaced? Visible dirt on the filter surface is not a good indicator. Air filters actually do a better job of trapping contaminants once they have been in operation long enough to gain a light coating of dust and dirt. To test an engine air filter, remove it from its housing and hold it up to a bright light such as 100-watt bulb. If light passes easily through more than half of the filter, it can be returned to service.

The light test works well with pleated paper filters. However, some cars have extended life engine air filters with dense fabric filtering media that are highly effective, but don’t allow light to pass. Unless a filter of this type is visibly caked with dirt, replace it at the mileage intervals specified by the vehicle manufacturer.

Some vehicles, primarily pickup trucks, have an engine air filter service indicator on the filter housing. This indicator measures the air pressure drop across the filter when the engine is running; the pressure drop increases as the filter becomes more restricted. Check the indicator at each oil change and replace the filter when the indicator says to do so.

Finding Quality Auto Repair

AAA recommends that you plan ahead for vehicle service by finding an auto repair shop and technician you can trust before you need them. AAA.com/Repair provides information on nearly 7,000 Approved Auto Repair facilities that have met AAA’s high standards for appearance, technician training and certification, insurance coverage and customer satisfaction. AAA regularly inspects every Approved Auto Repair facility and surveys their customers to ensure ongoing performance. In addition, AAA members receive special benefits that include auto repair discounts, an extended 24-month/24,000-mile parts and labor warranty, and AAA assistance in resolving repair-related issues.

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