DETROIT -- General Motors' sales sank 6 percent in January, a hangover from a year earlier when GM pumped up sales by piling on incentives.
GM sold 167,962 vehicles last month, with the total propped up by fleet sales.
U.S. sales chief Don Johnson said GM expected a decline in sales after a "very strong" January in 2011.
He was pleased that GM's U.S. market share in January likely held steady at around 18.8 percent, which would match its share for 2011, according to the Automotive News Data Center.
"Although those year-over-year sales changes look a little bit challenging, sequentially, our share of the business is very good news," he said. "Importantly, we delivered this result with incentive spending that is very competitive."
GM's incentives as a percentage of its average transaction price per vehicle was a hair under 10 percent, Johnson said. That was down nearly 3 percentage points from January 2011.
Truecar.com estimates that GM spent $3,095 per vehicle on incentives last month, down 16 percent from a year earlier.
GM's incentive binge in January and February of last year included a loyalty lease deal that allowed GM customers to waive the last three or four monthly payments if they bought new cars.
Since that binge, GM's incentive spending generally has been in line with the industry as a percentage of average transaction prices. Johnson said GM would continue to maintain "a level of discipline in our incentive spending" and match production to demand.
He added: "It doesn't mean that we're not going to do something in the market to try to take advantage of an opportunity."
Strength in January came from car sales and from a rise in deliveries to fleet customers.
GM sold 50,230 vehicles to fleets, which was 26 percent higher than GM's fleet sales a year earlier. Fleet sales accounted for 30 percent of GM's January sales, higher than the 26 percent for all of 2011.
Chevrolet sales slipped 1 percent, while GMC sales fell 10 percent. Sales dropped 23 percent at Buick and 29 percent at Cadillac.
GM's car sales rose 3 percent, led by the Chevy Cruze, up 10 percent; the Camaro, up 20 percent; and the recently launched Chevrolet Sonic, which totaled 5,712 sales, more than double the year-earlier tally for the car it replaced, the Aveo.
Meanwhile, sales of crossovers dropped 18 percent from a year earlier. Johnson blamed that partly on the phaseout of the HHR sports wagon. But some other previously brisk-selling crossovers in GM's lineup also lagged, including the Buick Enclave, down 28 percent and the Chevy Traverse, down 23 percent.