General Motors Co. downplays the impact of price discounting in last month’s U.S. sales jump of 22.7% vs. year-ago, yet the auto maker promises more “targeted” incentives as the months roll forward.

“I would characterize our incentive increase in January as modest,” says Don Johnson, GM’s U.S. sales chief.

“Our objective in January was to use our incentives to target conquest customers, as well as our existing customer base, as efficiently as possible,” he adds. “We were very successful. We did not expect our competitors to be as quiet as they were.”

GM spends an inordinate amount of today’s monthly sales call with journalists and Wall Street analysts explaining its incentive strategy in January, given reports of big increases from third-party information providers and its ugly history of discounting.

“There is a lot of noise out there,” Johnson says of reports showing GM’s incentive spending up as much as $400 in the month. “We do think fundamentally that our sales results and our financial results will tell the story for us.”

GM’s former practice of over-building to cover massive structural costs and discounting heavily to clear the resulting high inventories ate into profits and helped spin the auto maker into bankruptcy two years ago.

Out of Chapter 11 protection with a clean balance sheet, right-sized capacity and a more competitive labor agreement, GM promised new discipline in discounting.

“We’re not going to return to the days of driving production with incentives,” Johnson promises. “We know that is not going to be a recipe for success.”

At the same time, he says GM will continue to look for discounting opportunities while keeping inventories at historically low levels, despite growing demand.

“We did catch our competitors a little flat-footed in the month,” Johnson admits. “We continue to expect to put strategies in the market where we can win. We’re going to continue to be very judicious.”

He also says GM’s sales benefitted last month from bigger advertising spending focused on just four brands, compared with the days when the auto maker was forced to spread its dollars over eight divisions.

GM finishes January with an inventory of 509,822 vehicles, up -32% from 386,946 year-ago to reflect improving demand. However, stock levels during the incentive-fueled sales days before the auto maker’s bankruptcy often topped 1 million units.

Inventories at GM remain tight against growing demand, although stocks of its hottest sellers continue to build on recent production tweaks.

Brian Sweeney, who heads U.S. sales for GMC, says a move late last year to shuttle unfinished Chevy Equinox bodies from its Ingersoll, ON, Canada, assembly plant to nearby Oshawa for final assembly has boosted availability of the CUV and its GMC Terrain platform mate.

“Our dealers have seen huge relief on Equinox and Terrain (inventories) in the last 45, 60 days,” he tells Ward’s.

GM sells 178,897 units in January, compared with 145,832 year-ago, according to Ward’s data.

The auto maker says its retail sales grew 36% in the month, with fleet deliveries down 7% on a planned cutback in rental-fleet business and an uptick on the commercial side of 7%.

GM gets big numbers from some older models in the month, perhaps reflecting where it spent its marketing dollars.

The auto maker does not detail how much it discounts particular vehicles, but the Cadillac DTS large sedan saw sales jump more than 120% and its Buick Lucerne platform mate witnessed a 62% spike in deliveries.

Sales of the Chevy Impala midsize sedan grew 39%, and deliveries of the HHR cross/utility vehicle jumped 35%.

GM also posted solid increases across the board on large-truck sales, with the GMC Sierra pickup up 46% and deliveries of the Yukon and Chevy Tahoe SUVs rising 38% and 16%, respectively, Ward’s data shows.

Alan Batey, who heads U.S. sales for Chevrolet, says the new-for-’11 Cruze compact car also gained traction last month.

A slow ramp-up at its Lordstown, OH, assembly plant limited availability of the important new sedan. But in the last 60 days, GM has hit line speed and also made additional variants, such as a fuel-sipping Eco model and the least expensive base model, available to shoppers.

The Cruze accounted for 13,631 deliveries in January, and of that total 12,014 were at the more profitable retail end of the market. Last year, its predecessor, the Cobalt, posted 12,962 sales, of which 7,717 were fleet.

“We’re really starting to see our sales get established in the retail-car market,” Batey says.

GM wants a bigger piece of the passenger-car market after spending years relying on truck sales for profits.

Ward’s data shows the auto maker’s sales mix inching up to 37.4% cars in January after finishing 2010 with 36.5% of its deliveries in the segment. Ward’s counts CUVs as trucks.

GM also sold 321 units of its headline-grabbing Chevy Volt extended-range electric vehicle in January, on par with December when GM ramped up production.

“We’re selling every one we build, right in line with expectations,” Johnson says