GM said it had the best December in seven years, with a 19% year-on-year rise in US unit sales taking the company's total for 2014 to 2.94 million vehicles, a 4.8% rise.
Both for the month and the year, GM's Buick and GMC truck and sports utility vehicle (SUV) division led the gains, while its luxury unit Cadillac continued to drag, down 11.1% in the month and 6.3% for the full year.
Ford, the number-two automaker, said it enjoyed its best December in nine years, but unit sales were up just one percent from a year earlier.
For the year sales were virtually flat at 2.48 million vehicles, which the company blamed on a slowdown in pickup truck sales as it prepared the release late in the year of the new aluminum F-150, and on a deliberate cutback in sales to car rental agencies.
FCA US, the new name of the U.S. arm of Fiat Chrysler Automobiles, said its December turnover came in 20% above the previous year and marked a 10-year high, pushing the full-year 2014 sales to 2.09 million, a 16% rise from 2013.
Volume gains for all three U.S. automakers were strongest in the trucks and SUV categories, as cheap gasoline continues to mitigate the extra cost of the relatively low-mileage vehicles.
December sales for the industry appeared better than analysts had expected, and company officials forecast rising sales throughout 2015.
"The momentum the economy carried through 2014 accelerated in the fourth quarter," GM's chief economist Mustafa Mohatarem said.
"Car-buying fundamentals remain strong and we expect higher industry sales in 2015."
Copyright Agence France-Presse, 2015