The fuel economy for new cars sold in November averaged 25.3 mpg for the third straight month, according to a study conducted by researchers at the University of Michigan Transportation Research Institute.

Researchers Michael Sivak and Brandon Schoettle said the November average represents an improvement of 5.2 mpg compared to October 2007, when researchers started collecting data.

The university credited the unchanged average fuel economy to two trends: improved fuel economy of 2015 model-year vehicles, compared to 2014 models, and less demand for fuel-efficient vehicles due to decreasing price of gas.

UMTRI calculated average sales-weighted fuel economy from the monthly sales of light-duty vehicles (cars, SUVs, vans and pickups) and the combined city/highway fuel economy ratings that appear in the EPA Fuel Economy Guide and on vehicle window stickers to reach its figures.

The most recent UMTRI Eco-Driving Index revealed that the average emissions of greenhouse gases generated by the diver of a new vehicle stood still at 0.78. The figure shows that the average new-car driver produced 22 percent lower emissions than Oct. 2007.

The average price of a gallon of regular unleaded gasoline nationwide dropped to $2.78 on Thursday, down from $3.25 a year ago, according to the AAA Daily Fuel Gauge Report.

"Gas prices have fallen at a remarkable pace that would have been unthinkable just a few months ago," said AAA spokesman Avery Ash, in a company statement. "Lower gas prices represent real doorbuster savings as everyone begins their holiday shopping."

AAA believes that this year and in early 2015, gas prices will continue to drop based on low crude oil prices.

Click here to find gas prices near you.

The usual U.S. household purchases about 1,200 gallons of gas a year. Vehicle owners have purchased an average of $3.38 a gallon from January through November, according to MarketWatch.com.

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