Despite efforts to improve the fuel economy of large SUVs, their popular cuts into the U.S. national fuel economy average.

The fuel economy of new vehicles sold in the U.S. during November dropped by 0.1 miles per gallon to 25 mpg—the lowest mark this year, according to researchers at the University of Michigan Transportation Research Institute.

The value for November is up 4.9 mpg since October 2007 – the first full month of monitoring by UMTRI researchers Michael Sivak and Brandon Schoettle – but still down 0.5 mpg from the peak of 25.5 mpg reached in August 2014.

In addition to average fuel economy, Sivak and Schoettle issued a monthly update of their national Eco-Driving Index, which estimates the average monthly emissions generated by an individual U.S. driver. The EDI takes into account both the fuel used per distance driven and the amount of driving—the latter relying on data that are published with a two-month lag.

During September, the EDI worsened to 0.83 (the lower the value, the better)—up from 0.82 the month before.

(Production on the rise, keeping gas prices down. For the story, Click Here.)

The index currently shows emissions of greenhouse gases per driver of newly purchased vehicles are down 17%, overall, since October 2007—but 5 percentage points higher than the record low reached in November 2013.

The decline of both indexes assembled by UMTRI reflect the continuing growth in sales of trucks and utility vehicles, which generally are not as efficient as mid-sized and company passenger cars.

(Transportation eclipses power generation as leading cause of pollutions. Click Here for the story.)

However, Consumer Reports noted recently that the fleets of new sport utility vehicles unveiled for the Los Angeles Auto Show that automakers can meet the tougher fuel-economy standards by making gradual improvements

“The national fuel economy standards were designed to meet the market where it is and require automakers to improve their fleet, without affecting the size of vehicles they sell,” said Shannon Baker-Branstetter of Consumer Reports.

(To see why the average fuel economy of new vehicles is getting worse, Click Here.)

“The standards are flexible – meaning automakers don’t need to sell small sedans to meet their targets – they just have to make the vehicles they sell gradually more efficient. What we’re seeing with several of the early announcements is that the industry continues to innovate with new technologies that improve performance and efficiency for larger vehicles,” Baker-Branstetter added.