For years, experts including the Environmental Protection Agency told motorists to change their car’s engine air filter frequently for maximum fuel economy. However, a recent study funded by the U.S. Department of Energy found that air filter condition has no significant effect on the fuel economy of modern fuel-injected engines.
Automakers used to recommended air filter replacement at regular mileage intervals, but that practice failed to take into account the wide variety of real-world driving conditions. Two months driving in a dusty rural environment can cause the same amount of air filter restriction as a full year of vehicle use in a relatively clean urban setting.
Today, most automakers recommend that the air filter be inspected regularly, but replaced only when needed. More frequent replacement wastes money without improving fuel economy.
How do you know when a filter needs replacement? Visible dirt on the filter surface is not a good indicator. Instead, remove the filter and hold it up to a 100 watt light bulb. If light passes easily through more than half of the filter, it can be returned to service.
The light test only works with conventional pleated paper air filters. Some cars have extended-life factory filters with dense filtering media that are highly effective but do not allow light to shine through. Replace these filters at the mileage interval specified by the manufacturer.
A few vehicles, primarily pickup trucks, have a filter service indicator on the air filter housing. Check the indicator at each oil change, and replace the filter when the indicator says it is time to do 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. AAA Approved shops can be identified by the Approved Auto Repair sign, or by searching online at www.AAA.com/repair.
By John Nielsen AAA National Director of Auto Repair & Buying Programs For NewsUSA