Quick
acceleration and heavy braking can reduce fuel
economy by up to 33 percent on the highway and 5 percent
around town. New EPA tests account for faster acceleration
rates, but vigorous driving can still lower MPG.
Excessive
idling decreases MPG. The EPA city test includes
idling, but more idling will lower MPG.
Driving
at higher speeds increases aerodynamic drag (wind
resistance), reducing fuel economy. The new EPA tests
account for aerodynamic drag up to highway speeds of 80
mph, but some drivers exceed this speed.
Cold
weather and frequent short trips
can reduce fuel economy, since your engine doesn't operate
efficiently until it is warmed up. In colder weather,
it takes longer for your engine to warm, and on short
trips, your vehicle operates a smaller percentage of time
at the desired temperature. Note:
Letting your car idle to warm-up doesn't help your fuel
economy, it actually uses more fuel and creates more pollution.
Cargo
or cargo racks on top of your vehicle (e.g.,
cargo boxes, canoes, etc.) increase aerodynamic drag and
lower fuel economy. MPG tests do not account for this
type of cargo.
Towing
a trailer or carrying excessive weight
decreases fuel economy. Vehicles are assumed to carry
only three hundred pounds of passengers and cargo during
testing.
Running electrical
accessories (e.g., air conditioner) decreases
fuel economy. Operating the air conditioner on "Max"
can reduce MPG by roughly 5-25% compared to not using
it.
Driving on
hilly or mountainous terrain or on unpaved
roads can reduce fuel economy. The EPA test assumes vehicles
operate on flat ground.
Using 4-wheel
drive reduces fuel economy. Four-wheel drive
vehicles are tested in 2-wheel drive. Engaging all four
wheels makes the engine work harder and increases crankcase
losses.
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A
poorly tuned engine burns more fuel.
Improperly
aligned or inflated tires can lower fuel economy
by increasing rolling resistance.
Brake drag can make
your engine work harder.
A dirty air filter can decrease the fuel economy of older cars with carbureted engines.
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