Moving past the halfway mark of 2015, U.S. new-car average fuel economy hovered around 25 mpg, a recent analysis found.
The sales-weighted average window sticker fuel economy for new cars in June was 25.4 mpg, according to the University of Michigan Transportation Research Institute (UMTRI).
This represents a 0.1-mpg decrease from May, which researchers attribute to the continued strong sales of light trucks and SUVs.
However, overall fuel economy is still up 5.3 mpg since October 2007--when UMTRI began its monitoring.
June's average was 0.4 mpg lower than the peak value observed in August 2014.
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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In April--the most recent month with available data--the index was 0.85. That's an increase from March's 0.82, meaning U.S. drivers generated more emissions in April.
Estimated emission levels were unchanged for three months prior to this increase.
This value indicates that average new-car driver generated 15 percent lower emissions in April 2015 than October 2007--but 9 percent higher than the record low of August 2014.
Tracking new-car average fuel economy through May, the WardsAuto Fuel Economy Index appeared somewhat more optimistic.
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Cars posted an average 29.6 mpg, while light trucks reached 21.9 mpg. Both figures represent record highs, Wards says.
They also represent a 0.2-percent increase for cars and a 4.1-percent increase for light trucks over May 2014.
Average fuel economy across all new-vehicle segments was estimated at 25.5 mpg.
That's also an all-time high, as well as a 0.9-percent increase over the same period in 2014, and a 22-percent increase over the "base index score" set in the fourth quarter of 2007, according to Wards.
The industry trade journal also notes that light truck and SUV sales have increased in recent months.
But it claims the smaller, lighter segments within each vehicle type have gained market share at the expense of larger, heavier full-size vehicles.