By 2009, American car manufacturers were required to meet minimum fuel efficiency standards that increased the average miles per gallon to 27.5. By 2016, that standard increased to 39 mpg. What effect did this have?

Raising the fuel-efficiency standard from 27.5 to 39 miles per gallon means cars travel farther using the same amount of fuel. That reduces fuel and energy consumption per mile, so the best answer is decreased energy consumption.

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