As we say goodbye to March, the month has brought some good news: The average fuel economy of new vehicles rose to a new high.

According to researchers at the University of Michigan Transportation Research Institute (UMTRI) the sales-weighted average fuel economy of all new light-duty vehicles sold in the United States last month was 25.4 mpg.

After a slight dip in December 2013, average new-car fuel economy has been rising steadily since the beginning of the year. March's average, an all-time high, represented an increase of 0.4 mpg over January's number.

While only a quarter of the year has passed, carmakers are on track to set another average gas-mileage record in 2014. The current three-month average is already 25.1 mpg, compared to 24.8 mpg for the entirety of 2013.

Fuel Gauge

Fuel Gauge

Another record year wouldn't be unusual. In fact, it would be typical: fuel economy has consistently improved year-to-year since UMTRI began collecting data in 2007.

UMTRI's sales-weighted average covers all new vehicles, from subcompacts and midsize sedans to full-size pickup trucks and SUVs, which is why the number is relatively low.

Fuel-efficiency numbers are available for nearly all new vehicles sold. Model years are assumed to run from September of the previous year to August of the calendar year.

UMTRI also calculates what it called the Eco-Driving Index, which estimates the monthly greenhouse-gas emissions produced by the average individual U.S. driver.

The index--based on gas mileage and miles driven--was at 0.80 for January 2014, the most recent month with available data.

That matches the yearly average for 2013, and represents a 20-percent decrease in emissions since UMTRI began measuring in October 2007.

The continuous improvement in fuel economy isn't surprising, as automakers try to keep up with stricter government fuel-efficiency requirements.

The EPA and NHTSA announced a stricter set of rules for model years 2012 to 2016 back in 2010, even more stringent rules will take effect for model years 2017 through 2025.

In addition to internal-combustion fuel-economy improvements, the increase has also been boosted by growing sales of plug-in electric cars, a trend that's expected to continue through 2014.


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