From its striking design to its pulsating TV spots, the LaCrosse marks a decidedly different direction for Buick.

And that’s just on the surface. The change gets even starker under the hood, where for the first time in a decade, the brand will offer a four-cylinder engine, as General Motors works to meet stiffer fuel-mileage standards expected for 2016. Buick also will offer all-wheel drive in the LaCrosse, the first time it’s ever put that technology in a sedan.

The redesign for 2010 brings a lot of change for a brand that has become fairly stodgy in the marketplace. But that’s the idea, says Susan Docherty, vice president of Buick-Pontiac-GMC in North America.

“We’re working hard to change the perception of the brand and to let people know Buick may not be what they think it is,” she said in a Web chat with journalists Monday.

The LaCrosse will begin arriving at dealerships at the end of this month, and V6 models will start at $27,835, including shipping charges. The V6s are versions of the same engines that appear in a range of GM vehicles, including the Cadillac CTS and SRX and the Chevrolet Camaro. Using variable valve timing and direct injection, the 3.6-liter unit makes 280 hp, while the 3.0-liter is rated at 255 hp for front-wheel-drive versions.

The four-banger is thought to be the first in a Buick since the 1998 Skylark. It’s from GM’s Ecotec family and makes 182 hp and 172 lb-ft of torque. It’s an inline setup and employs direct injection; look for it to get an estimated 20 mpg in the city and 30 mpg on the highway.

The LaCrosse is a global blend of GM engineering and design resources. The interior, which features ice blue ambient lighting, Bluetooth connectivity and in-dash navigation, is a collaboration between American and Chinese designers. The platform was borrowed from the Opel Insignia, produced by GM’s European arm.

The chief competitor will be the Acura TL, while the Lincoln MKZ, the Lexus ES350, the Chrysler 300, the Toyota Avalon and the Ford Taurus also are expected to draw comparisons, officials said.

GM brass say they hope that the LaCrosse can continue the ongoing facelift for Buick and point to the path set by the Enclave. The median age of buyers of the handsome crossover is 12 years younger than the brand’s typical demographic, and Buick is planning a social-media component of its advertising to try to reach untraditional buyers in their 20s.

“Today, many people perceive Buick as a great brand with good quality and a high level of craftsmanship,” Docherty said. “However, they see it as a brand that’s ‘not for me.’ What started with the Enclave in terms of changing perceptions needs to continue with the LaCrosse.”

Meanwhile, Buick officials remain mum on how the brand might be fleshed out, noting that the Regal that has shown up in some advertisements is a concept (though it’s on sale in China) and saying it is unlikely that the Pontiac G8 would be rebadged.