Currently the CAFE standards have been defined and administered as a
5% annual increase in vehicle fuel mileage resulting in 35.5 MPG by the year 2016.Now it's being said that if the fuel mileage requirements are increased 6% annually beginning in 2017 that the CAFE fuel mileage will be 62 MPG by the year 2025. Or a 5% increase in annual CAFE standard beginning in 2017 would produce 47 MPG by the year 2025.
But this is the wrong way of doing things and actually proved by the history of the late 1970's and early 1980's when vehicle drive-ability become poor due to emission limits. The problem is that incremental increases in requirements encourge immediate and short term bandaid solutions and then bandaid solutions on top of previous bandaid solutions.
The correct way to implement the CAFE standards would be to simply require CAFE fuel mileage of 35.5 MPG at the year 2016. And then require 47 MPG at the year 2025. This strategy would allow long term design projects to fully develop a roll-out of a comprehensive technology and avoid the side effects of implementing and abandoning lessor technologies.
Is 47 MPG in the year 2025 possible ? Certainly, mid-size cars weighing 2400 pounds and using 1.6 engines would do their part in meeting the average. (Engine power has increased with direct fuel injection instead of port fuel injection and so a 1.6 engine can be equal to a 1.8 engine.) It's just hard for the average person to visual a mid-size car that is not smaller but that weighs 1000 pounds less. But plastic bodywork and floorpans are both bodywork and insulation. Then the frames could be hydroformed aluminum like in the Z06 Corvette. Finally, a car that loses 500 pounds in weight can use a smaller engine and transmission and then lose another 150 pounds in weight. Oops, I only reduced the 3400 pound mid-size car to 2750 pounds.