The sales-weighted average fuel economy of new cars and trucks sold in the U.S. declined last month, although it remains high overall.
Average window-sticker fuel economy for new vehicles in April was 25.2 mpg, representing a decrease of 0.2 mpg from March.
This information comes from the University of Michigan Transportation Research Institute (UMTRI), which tracks fuel economy on a monthly basis.
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April's sales-weighted average was down 0.6 mpg from the peak reached in August 2014.
However, overall fuel economy is still up 5.1 mpg from October 2007--the first month of monitoring by UMTRI researchers.
In addition, average fuel economy for the first seven months of the current model year--considered to begin in October 2014--is 25.3 mpg.
The UMTRI also calculates an Eco-Driving Index, which estimates the average monthly emissions of greenhouse gases generated by an individual U.S. driver.
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For February--the most recent month with available data--the index was 0.82, the same as the value for January. Lower numbers equal lower estimated emissions in this case.
That value indicates that the average new-vehicle driver generated 18 percent lower emissions in February 2015 than in October 2007.
UMTRI researchers attribute April's drop in average fuel economy to increased sales of trucks and SUVs.
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Yet while consumer trends may drive the average fuel economy of vehicles sold in a given month down, it should continue to trend upward over the long term.
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That's because carmakers will have to continue improving fuel economy across their lineups to meet Corporate Average Fuel Economy (CAFE) standards.
These standards mandate a fleet average of 54.5 mpg by 2025, which is equivalent to about 40 mpg on the window sticker.