"Many factors have helped car sales recently," says Edmunds.com analyst Jessica Caldwell, in a prepared statement. "Low gas prices, a record stock market and the improving economy are making people feel more financially comfortable, and even the weather has cooperated, for the most part."
Sales also benefited because December 2014 had 26 sales days, one more than 2013.
Kelley Blue Book forecast a 9.8% gain to 1.49 million units sold. Edmunds forecast an 11.4% gain to 1.5 million vehicles sold. And J.D. Power also forecast sales of 1.5 million.
For the month, Fiat Chrysler (FCAU) is expected to lead the pack. Edmunds has Chrysler sales up 25% for the month, and Kelley Blue Book sees a 20.5% gain. That would lead to a market share of 14.2%, up a full percentage point for the year.
"Toyota has had a quietly solid year with strength in line with the industry, but it currently has two of the top three selling cars with its Camry and Corolla, which are up 5% and 11% respectively this year," Kelley Blue Book said.
As for Ford, its transition to the 2015 F-150, which is beginning to reach dealerships, will be closely watched. The model changeover in the best-selling U.S. vehicle means December will belong to competitors.
"Full-size trucks should experience a normal seasonal spike in December, which is aided by gas prices at a five-year low," said Kelley Blue Book analyst Alec Gutierrez, in a prepared statement. "As the all-new Ford F-Series begins to make its way to dealerships, General Motors and Fiat Chrysler stand to gain the most sales in December."
Based on its December forecast, Edmunds said overall U.S. light vehicle sales will rise 6% in 2014 to 16.5 million units. U.S. spending on new cars is expected to have risen from $90.8 billion in 2013 to approximately $100 billion in 2014.