For Modern Cars, Replacing an Air Filter Will Improve Performance but Not Fuel Economy
April 27, 2009
A February 2009 study conducted by Oak Ridge National Laboratory found that for modern computer-controlled, fuel-injected engines, changing a clogged air filter has no measurable affect on fuel economy but does affect ultimate performance. Average acceleration times for the vehicles in the study improved by 6 to 11 percent when running on a clean filter. The fuel economy of carbureted engines, which went out of production in the early 1980s, was impacted by a dirty air filter. The study found that typical fuel economy gains for replacing the air filter on the carbureted vehicle were in the range of 2 to 6 percent.
Performance Benefit to Changing a Clogged Air Filter on a Modern Vehicle
WOT* Acceleration Test Results (0-60 mph), New vs. Clogged Air Filter
| Test Vehicle | New Air Filter (sec) | Clogged Air Filter (sec) | Difference (sec) | Difference (%) |
|---|---|---|---|---|
| 2003 Toyota Camry | 17.24 | 18.51 | 1.26 | 7% |
| 2007 Buick Lucerne | 13.77 | 15.45 | 1.68 | 11% |
| 2006 Dodge Charger | 10.23 | 10.84 | 0.61 | 6% |
* WOT = Wide-open throttle.
Notes
- WOT – Wide-open throttle
- MPH – Miles per hour
- A clogged filter was defined by a level of airflow restriction that was sufficient to activate a common indicator light inside the vehicle showing the air filter needs changed. On all vehicles, the level of restriction was on the order of 6.0 to 7.0 kilopascals (kPa – pressure unit).
Source
Kevin Norman, Shean Huff and Brian West, Effect of Intake Air Filter Condition on Vehicle Fuel Economy, Oak Ridge National Laboratory, Report: ORNL/TM-2009/021, February 2009.