That shift is roiling the luxury segment. Since the top luxury makes depend heavily on sedans, the shift to trucks is hitting them harder than other manufacturers. The largest players rely heavily on sport sedans. In December, luxury car sales fell 11 percent, while premium crossover and SUV sales climbed 22 percent.
The fallout was most painful for the BMW brand. Its total volume fell 17 percent, caused by a 27 percent plunge in car sales. Light trucks, which make up only about a third of total BMW brand sales, rose 6.4 percent.
Lexus faces a similar challenge but is less tied to cars than BMW, getting more than half of its sales from light trucks. As a result, total Lexus sales rose 3.8 percent last month. The compact NX crossover helped boost Lexus crossover and SUV sales 6.6 percent.
Mercedes' total volume was up 2.6 percent, but only 0.6 percent when excluding the Sprinter commercial van. Its light-truck sales climbed 25 percent, excluding Sprinter, offsetting a 15 percent drop on the car side.
Thanks to its strong December, Lexus reasserted itself in the luxury sales race in 2015, finishing slightly ahead of Mercedes, excluding Sprinter, and just behind BMW, which won for the fourth time in the last five years.
The consumer shift to trucks, however, poses longer term challenges for the top luxury makes. In sport sedans, they hold a clear advantage over most competitors, but it's a different matter in crossovers.
Acura's ILX compact sedan, for example, is not really a threat to the BMW 3/4 series or Mercedes C class. But together Acura's MDX and RDX crossovers often outsell BMW's X3 and X5.
In a similar way, Volvo is a bit player in luxury cars, but its redesigned XC90 is rolling. The company sold 3,135 XC90s in December, up from 68 a year before.
"As you move into crossovers, the competition gets much tougher for the luxury players," said Jim Ursomarso, vice president of Union Park Automotive Group in Wilmington, Del.
Brands such as Jeep, GMC and Subaru also offer credible alternatives to higher-priced BMW and Mercedes crossovers, he noted.
"The X3 can easily run over $40,000 with options," Ursomarso said.
"The GMC Terrain is a very popular vehicle, and you can get it for quite a bit less than an X3."