Calculating a car’s CO2 emissions from its mpg | ETA This is handy. To get CO2 g/km, divide the MPG petrol into 6760 or divide MPG diesel into 7440. CAFE PIC Fleet In 2016, the US fleet CAFE standard was 32.7 MPG. This is equivalent to 206.7 g/km. The CAFE standard would need to jump up to 71.2 MPG (nearly double!) to be at parity with the EU 95 g/km.