MPG history

A decade earlier, the 1985 Dodge Diplomat also managed to get a worse gas mileage rating at 12 mpg.

In 1986, the penalty was raised to $3,850 for cars rating under 12.5 mpg.

Finally, in 1989, NHTSA restored the 27.5-mpg passenger-vehicle standard but lowered light-truck requirements to 20 mpg.

Widely accepted as the worst compact car for gas mileage, the 1995 Saab 9000 only got about 18 mpg city.

After Congress lifted the freeze on fuel economy in 2000, the administration enacted a pair of minimal light-truck increases.

In 2002, the National Academy of Sciences reported that cars and trucks could meet a 37-mpg fleet-wide standard within 10 to 15 years without sacrificing performance or safety.

In December 2007, Congress passed the first changes to United States fuel-economy standards in nearly 20 years.

Actual on-road fuel efficiency is lower--24.1 m.p.g. for cars and 18.1 m.p.g. for trucks in 2008

In April 2009, President Barack Obama accelerated the increase in the previous administration's CAFE standards.

Medium and heavy duty vehicle draft rule: In October 2010, the administration proposed the first joint fuel efficiency and tailpipe emission standard for medium and heavy duty trucks.

Medium and heavy duty vehicle final rule: In August 2011, the EPA and NHTSA announced the final joint fuel efficiency and tailpipe emission standards for heavy duty vehicles.

Increasing at an average of 5 percent annually, most passenger cars must achieve 39 mpg, and light trucks 30 mpg, by 2016.

Covered vehicles would be separated by type and fuel, with fuel-economy improvements of 20 percent for combination tractors, 10 percent for gasoline trucks and vans, and 10 percent for diesel trucks and vans and all vocational vehicles (such as dump trucks and cement mixers) by model year 2018.