Fuel Economy Estimates

For a lot of vehicles you can see in these
days estimates how much gas a car needs
when driving an amount of miles per used
gallon of gas. Usually the car driver has
to differentiate between two fuel economy
estimates.
City represents urban driving, in which a
vehicle is started in the morning
(after being parked all night) and
driven in stopand-go rush hour traffic.
Highway represents a mixture of rural
and interstate highway driving in a warmed-up
vehicle, typical of longer trips in freeflowing traffic.
Cars, tested by the EPA (Environmental Protection
Agency, are lab tested. The EPA miles-per-gallon (MPG)
estimates are based on lab testing and are adjusted
downward by about 15% to better reflect realworld
driving conditions for an average U.S. motorist.
Vehicles are tested in the same manner to allow fair comparisons.

Why Your Fuel Economy Will Vary

Your vehicle’s fuel economy will almost
certainly vary from all fuel economy ratings.
Fuel economy is not a fixed number;
it varies significantly based on where you
drive, how you drive, and other factors.
Thus, it is impossible for one set of estimates
to predict fuel economy precisely for all drivers
in all environments.
For example, the following factors can lower your
vehicle’s fuel economy:
• Aggressive driving (hard acceleration and braking)
• Excessive idling, accelerating and braking
in stop-and-go traffic
• Cold weather (engines are more efficient
when warmed up)
• Driving with a heavy load or the air
conditioner running
• Improperly tuned engine, dirty air filter,
under-inflated tires
Small variations in vehicle manufacturing
can cause MPG variations in the same make
and model, and some vehicles don’t attain
maximum fuel economy until they are “broken in”
(around 3,000-5,000 miles).
So please remember that the fuel economy
ratings are a useful tool for comparing vehicles
when car buying, but they may not accurately
predict the MPG you will get.
This is also true for annual fuel cost estimates.