About the Fuel Economy Data
Scientific models suggest that increased buildup of greenhouse gases in the atmosphere will
raise the earth's temperature and change the earth's climate. The buildup is largely due to the release of
carbon dioxide (CO2) upon burning fossil fuels, such as coal and oil, to power
industries and transportation. CO2 levels in the atmosphere have fluctuated
significantly before the advent of human industrialization; nonetheless, data suggest that the current buildup
of CO2 is happening much faster than at any time in the past 10,000 years.
Such a rapid change is likely to produce more extreme weather, rising sea levels that erode coastal areas and contaminate
fresh water supplies, threats to agriculture and wildlife, and public health risks from infectious disease and
In the US economy, the transportation sector accounts for 32.6% of all CO2 emissions. (The production from other sectors is as follows: commercial: 16.0%, Industrial:
32.2%, and residential: 19.2%.) The US Department of Energy claims that every gallon of gasoline your
vehicle burns puts 20 pounds of carbon dioxide into the atmosphere, and that choosing a vehicle that gets 25 rather
than 20 miles per gallon will prevent 10 tons of carbon dioxide from being released over the lifetime of your vehicle.
Consequently, consumers can greatly influence the amount of CO2 emissions by making
smart choices about the automobiles they drive.
This data set suggests that there is a relationship between engine size and fuel economy,
thus one might expect a relationship between engine size and CO2 emissions.
Note that the gasoline powered cars selected in this data set are of several classes, subcompact, minicompact
and compact, so there is some variability in their size and weight. Because data on engine size and gas mileage
are not for the same vehicle, it is difficult to conclude that a given change in engine size for any one vehicle
will result in a specific increase or decrease in highway mileage. In general though, driving a vehicle with
a smaller engine will more likely consume less gasoline and produce fewer emissions. Students can fit a curve
(trendline) through the data with software such as Excel or Minitab and determine a mathematical relatioship between
engine size and highway mileage; a power law regression model has an R2 of about 0.7.
In addition to reducing CO2 emissions, the purchase of higher
mileage vehicles will reduce oil imports, conserve fossil fuel resources for future generations, reduce other harmful
emissions such as CO, NO, and NO2 , and save consumers money in gasoline costs.
To calculate the savings in running a more fuel efficient car, visit the website http://www.fueleconomy.gov/feg/savemoney.shtml.
Reference for data: Model Year 1999 Fuel Economy Guide, United States Department of Energy.