Under New EPA MPG Method, All Estimates Drop; Hybrids Retain Most of Their Advantage Relative to Conventional

26 February 2007

Hybrids retain most of their fuel economy advantages over their conventional counterparts under the new EPA method for estimating mpg, despite a decrease in the estimate resulting from the new method. Click to enlarge.

The EPA has published estimates of the affect of the revised methods for estimating vehicle fuel economy—which apply to model year 2008 and later vehicles—on earlier model year cars as a way to educate consumers on the likely impact of the changes.

Compared to today’s estimates, the city mpg estimates for the manufacturers of most vehicles will drop by about 12% on average, and by as much as 30% for some vehicles. The highway mpg estimates will drop on average by about 8%, and by as much as 25% for some vehicles. (Earlier post.)

Although the fuel economy estimates for hybrids drop along will those for all vehicles, hybrids appear to retain the majority of their fuel economy advantage compared to their conventional counterparts.

While the combined mpg estimate for the 2007 Camry hybrid, for example, drops 13% from 39 mpg under the old method to 34 mpg under the new, the hybrid’s efficiency advantage compared to its conventional cousin only decreases 3 percentage points from 39% to 36%.

The 2007 Prius, with no conventional model for comparison, would take a 16% hit in combined fuel economy under the new method, dropping from 55 mpg to 46 mpg. Its city driving score suffers the most, dropping 20% form 60 mpg under the old method to 48 mpg under the new. Highway driving drops 12% from 51 mpg to 45 mpg.

The new EPA methods include the city and highway tests used for previous models along with additional tests to represent faster speeds and acceleration; air conditioner use; and colder outside temperature. MPG estimates will also be adjusted downward to account for factors that are difficult to replicate in a laboratory, such as wind and road surface resistance.

EPA has put a comparison tool on its Fuel Economy site to allow consumers to see an estimated outcome of the new method on older vehicles.