If the US fleet of vehicles were mandated to become 33 more

If the U.S. fleet of vehicles were mandated to become 33% more fuel efficient, how much annual emissions of CO_2 would that prevent (tons/yr)? Assume the following: Currently there are 250 million vehicles in the U.S., each driving (on average) 12, 500 miles/year, with an average fuel economy of 18 mi/gal. Also, assume each gallon of gasoline contains about 5.0 lb of carbon.

Solution

Total vehicles= 250 millions

Total miles covered=250*12500 million=3125000 million miles

Total fuel consumed= 3125000 million/18 gallons= 173611.11 million gallons.

Now of vehicles become 33% fuel efficient increase in mileage = 5.94 miles

To cover 3125000 miles fuel now the fuel required is 3125000 million/(18+5.94)=130534.67 gallons

Fuel savings=173611.11 -130534.67 million gallons

Fuel savings=43076.44 million gallons

Now total CO2 emissions which would be prevented are 43076.44 *5= 215382.2 million pounds of CO