According to a new report from the International Council on Clean Transportation, the gap between rated fuel efficiency and the real-world gas mileage achieved by actual drivers is increasing.
Get more information on U.S. and European real-world fuel ratings.
According to a new report, the gap between rated fuel efficiency and the real-world gas mileage achieved by actual drivers is increasing.
In 2001, it notes, the average difference between rated gas mileage and actual results was 20 percent or less in the U.S. and 10 percent or less in Europe.
By 2012, that gap had risen to 35 percent in the U.S. In Europe, it was 25 percent in 2011.
The bulk of its analysis applies to European cars and drivers, using data gathered from fleets in Germany, the Netherlands, Switzerland, and the U.K.
It shows the steepest increase in 2007 and 2008, when several member countries switched to taxing cars based on their rated tailpipe emissions of carbon dioxide.
The report is careful to note up front that “nothing in this analysis suggests that manufacturers have done anything illegal.”
Only four pages of the 88-page report apply to similar discrepancies in the U.S.
That analysis is based on variations in “My MPG” data submitted by users to the EPA’s FuelEconomy.gov website starting in 2004, against the official EPA fuel efficiency ratings.
The report suggests that more study is needed on these discrepancies.
“For the United States,” it concludes, “the data examined in the context of this paper are seen only as a starting point for future analysis.”