Primer on Automobile Fuel Efficiency and Emissions - Pollution Probe

CHAPTER 2 | AUTOMOBILE ENERGY USE, EFFICIENCY AND EMISSIONS EXPLAINED
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Automobiles work by converting energy provided by fuel into motion at the
wheels. The further an automobile can travel on a given amount of fuel, the
more efficiently it is considered to have provided this service. Automobiles that consume less fuel in operation
than others are, therefore, considered to be more fuel efficient.
Fuel efficiency is most commonly measured in the U.S. as fuel economy or mileage (miles driven per US gallon
consumed, or mpg) and in Canada as fuel consumption (litres consumed per hundred kilometres traveled, or
L/100km). As fuel efficiency improves, fuel economy increases (i.e., you can travel farther on the same amount
of fuel) but fuel consumption decreases (i.e. you use less fuel to travel the same distance). Note, however, that
changes in fuel efficiency are not represented in the same way for
each standard of measurement. For example, a one-third increase
in fuel economy (i.e., 33 per cent increase) is the same as a onequarter
reduction in fuel consumption (i.e., 25 per cent reduction).
A 100 per cent increase in fuel economy (i.e., a doubling) equals a
50 per cent reduction in fuel consumption (i.e., a halving). See Box
2-1 for further discussion on the differences in working with
both measures of fuel efficiency.
To convert from miles per US gallon
to L/100 km, divide 235 by the mpg
value.
To convert L/100 km to miles per
US-gallon, divide 235 by the L/100km
value.
Use the figure 282 for miles per
imperial gallon which is about 20
per cent larger than the US gallon.
<strong>Primer</strong> on Automobile Fuel Efficiency & Emissions
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