Experts including the Environmental Protection Agency have been telling motorists to change their vehicle’s air filter often for maximum fuel efficiency for many years. Recent research funded by the U.S. Department of Energy has shown that the condition of the air filter does not have any significant impact on modern fuel-injected engine’s fuel economy.

Although automakers recommended replacing air filters at regular mileage intervals, this practice did not take into account the many driving conditions. Air filter restriction can be as severe in rural areas where vehicles are used for two months, as in urban settings that are clean and well-maintained.

Most automakers recommend that air filters be checked regularly and replaced when necessary. Regular replacement is a waste of money and does not improve fuel economy.

How do you tell when your filter needs to be replaced? Visible dirt on the surface of the filter is not an indicator. Instead, take the filter out and place it in front of a 100-watt light bulb. If the filter is visible through less than half of it, you can return it to service.

Only conventional pleated paper air filter types are eligible for the light test. Some cars come with extended-life factory filters that are densely filtered media but still allow light through. These filters must be replaced every 2,000 miles.

Some vehicles, especially pickup trucks, include a filter service indicator on their air filter housing. The indicator should be checked at every oil change and replaced when it says so.

For non-do-it-yourselfers, the certified technicians at more than 8,000 AAA Approved Auto Repair facilities across North America will be happy to help with air filter inspection and replacement, along with any other automotive maintenance and repair needs you may have. You can identify AAA Approved Shops by looking online or using the Approved Auto Repair sign. www.AAA.com/repair.

John Nielsen joined AAA in 1998 as the national director for the Approved Auto Repair network. Nielsen has over 30 years of automotive industry experience. He holds an ASE Master Automotive Technician certificate and authored the book. “Making Sense of Car Care,”As Editor in Chief of AAA’s new truck and car reviews, he has testified before the state and national legislatures. He is a frequent guest on national TV and radio shows.