Air Filters and Fuel Economy

Replacing Clogged Air Filter Improves Performance but Not Gas Mileage
for Modern Cars 

 

If you've been changing your car's air filter regularly hoping to save a
little money at the gas pump, the engineers at Oak Ridge National
Laboratory (ORNL) have some bad news for you. Unless you're driving an
old carbureted car from the 1970s, changing that air filter may get you
more pep, but it won't save you any gas money.

 

A new study conducted by ORNL and sponsored by the Department of Energy
(DOE) determined that replacing a clogged air filter on a modern
gasoline vehicle with a fuel-injected, computer-controlled engine-the
kind prevalent in vehicles manufactured since the early 1980s-has no
measurable effect on fuel economy. It can, however, improve your
acceleration noticeably. Average acceleration times for vehicles in the
study improved by 6 to 11 percent when running on a clean filter. 

 

If you're hoping to get better gas mileage from an older car or truck,
changing the air filter may not be a bad place to start. The study
showed that replacing a clogged filter on a car with a carbureted engine
could improve fuel economy up to 14 percent if the filter is so clogged
that it significantly affects drivability. Fuel economy gains for
replacing an air filter under more typical conditions on the carbureted
vehicle tested were in the range of 2 to 6 percent. 

 

This study is the first from an ongoing program-sponsored by DOE's
Office of Energy Efficiency and Renewable Energy (EERE)-aimed at
updating and verifying gas mileage tips. The program is conducted in
support of the fueleconomy.gov Web site, the federal government's
authoritative source for fuel economy information, which DOE co-hosts
with the Environmental Protection Agency (EPA). Prior to the ORNL study,
fueleconomy.gov advised consumers that changing a clogged air filter can
improve fuel economy by up to 10 percent. This advice was based on a
study that pre-dated the widespread use of fuel-injected,
computer-controlled engines in most passenger vehicles. The new study
was conducted to determine whether this fuel economy tip applied to
these modern engines. 

 

Questions about the study should be directed to Brian West, Oak Ridge
National Laboratory, 865-946-1231, westbh@ornl.gov. ORNL maintains
fueleconomy.gov for the DOE and EPA. Fueleconomy.gov provides consumers
with EPA fuel economy estimates for cars and trucks back to model year
1985, vehicle tax incentives, tips for improving fuel economy, and other
information. The new fuel economy tip and ORNL's technical report Effect
of Intake Air Filter Condition on Vehicle Fuel Economy are available at
http://www.fueleconomy.gov/feg/maintain.shtml.

 

Bo Saulsbury

Oak Ridge National Laboratory

Environmental Sciences Division

P.O. Box 2008

1 Bethel Valley Road

Oak Ridge, TN  37831-6335

(865) 574-4694