Less than five years after President George W. Bush signed the Energy Independence and Security Act into law―increasing the federal Corporate Average Fuel Economy standard for the first time in nearly two decades―new data from University of Michigan’s Transportation Research Institute (UMTRI) indicates that the average new vehicle purchased in the United States has become nearly 20 percent more efficient since fall of 2007. According to UMTRI’s numbers, the average fuel economy of a new car sold in the U.S. was 24.1 mpg in March, compared to 21.2 mpg in March of 2008 and just 20.1 mpg in October of 2007.

The increase has been particularly rapid of late, as gas prices rise and carmakers introduce an ever-widening array of fuel-saving options ranging from electric vehicles, to hybrids, to clean diesels, to efficient gas cars. Four years ago, when oil prices spiked to unprecedented levels, few major automakers had much to offer customers looking for significant gas savings. With the new CAFE standards in place, carmakers have scrambled to get every last mile out of a gallon of gas, and have been particularly successful in implementing engine technologies like turbocharging and direct injection to provide both more power and better efficiency in some models than their predecessors.

One company that has been particularly successful in this area is Ford. In just the last year Ford has seen the average fuel economy of its cars and trucks jump by nearly 5 mpg, thanks in part to the success of the carmaker’s new EcoBoost truck engine, which increases efficiency 20 percent, while increasing power. Ford has sold more than 100,000 EcoBoost engines in its F-150 trucks in the last twelve months.

In addition to improved drivetrain efficiency, fuel economy is also rising because consumers are choosing smaller vehicles. An increase in the sales of compacts and subcompacts, as well the rise of crossovers to replace SUVs in many garages has been a gradual trend on the list of monthly sales leaders for some time now.

The current high-water mark for CAFE is 54.5 mpg by 2025, a number announced last year by the Obama administration, meaning that carmakers will continue to have to give consumers more and more affordable fuel-efficient options if they want to remain in compliance with the law. So long as fuel prices continue to rise, drivers can probably be expected to embrace those options.