General Motors Co's premium Buick brand is drawing younger customers with its newer lineup of vehicles, a top executive said on Tuesday.

Buick, which said last month it will introduce four new or refreshed models in the U.S. market in the next 12 months, has seen the average age of its buyers drop to 57 from 64 five years ago, said Tony DiSalle, Buick marketing vice president.

"There's a lot of really strong momentum," he told reporters at an event outside Detroit. "People are seeing the product portfolio. It's changing their perception of what Buick is in a very good way."

Buick's U.S. sales rose 8 percent in September, but are down 2 percent in the first nine months on cutbacks on fleet sales to commercial customers.

The brand, which sells the Verano compact, and LaCrosse and Regal mid-sized cars and Enclave crossover, will add the Encore small crossover late in the first quarter of next year. Newer versions of the LaCrosse, Regal and Enclave are also coming.

Research firm LMC Automotive expects Buick's U.S. sales to rise almost 4 percent this year to about 184,500 vehicles and hit more than 263,000 in 2015.

Buick sales in China, which accounted for about 77 percent of the brand's global total last year, are expected to increase 4 percent to about 672,600 this year and reach almost 835,000 in 2015, LMC said.

While DiSalle did not disclose a future target for the average buyer's age, he said it would likely come down further once the Encore hits the U.S. market.

Buick's conquest rate, or the percentage of buyers who are new to GM cars, stands at 43 percent for the year to date and has been even higher in the last few months, above 45 percent, as the supply of the newer Verano increases.

The lease penetration rate has risen, hitting 36 to 37 percent, up from 15 percent at the start of the year, DiSalle said. The brand's "Experience Buick" 24-month lease program, launched in March deserves the credit, he said.

Under the program, customers receive free maintenance, as well as satellite radio and GM's OnStar communications, in-vehicle safety system.

DiSalle declined to say when the lease program would end, but added there are no current plans to discontinue it. "We have every intent to keep it going," he said. (Reporting By Ben Klayman in Birmingham, Michigan; Editing by Tim Dobbyn)