U.S. Department of Energy - Energy Efficiency and Renewable Energy
Vehicle Technologies Office
Fact #568: April 27, 2009
For Modern Cars, Replacing an Air Filter Will Improve Performance but Not Fuel Economy
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 
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).
Supporting Information
Acceleration times 20 to 80 MPH at WOT* (Seconds)
| |
Difference |
| Test Vehicle |
New Air Filter |
Clogged Air Filter |
Seconds |
Percent |
| 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% |
|
* Wide-open throttle.
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 (PDF 1.0 MB). Download Adobe Reader. |
Return to 2009 Facts of the Week
|