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An increase in fuel economy by 5 miles per gallon (mpg) does not translate to a constant fuel savings amount. Thus, trading a low-mpg car or truck for one with just slightly better mpg will save more fuel than trading a high-mpg car or truck for one that is even higher. For example, trading a truck that gets 15 mpg for a new one that gets 20 mpg will save 16.7 gallons of fuel for every 1,000 miles driven. In contrast, trading a 35 mpg car for a new car that gets 40 mpg will save 3.6 gallons of fuel for every 1,000 miles driven. These fuel savings are additive; that is, going from 15 mpg to 25 mpg saves 26.7 gallons per thousand miles driven — 16.7 gallons (15-20 mpg difference) plus 10.0 gallons (20-25 mpg difference).

Fuel Savings per Thousand Miles
Bar graph showing gallons of fuel saved per 1.000 miles when trading a truck or vehicle for one with slightly better gas mileage. For more detailed information, see supporting information below.

Supporting Information

If you have a car with this fuel economy... And you trade it for a car with this fuel economy... You save this many gallons for every 1,000 miles you drive
5 mpg 10 mpg 100.00
10 mpg 15 mpg 33.3
15 mpg 20 mpg 16.7
20 mpg 25 mpg 10.0
25 mpg 30 mpg 6.7
30 mpg 35 mpg 4.8
35 mpg 40 mpg 3.6
40 mpg 45 mpg 2.8
45 mpg 50 mpg 2.2
50 mpg 55 mpg 1.8
55 mpg 60 mpg 1.5

Source:
U.S. Department of Energy and Environmental Protection Agency, Fuel Economy Guide Website.

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