There's a digital twist to the automobile test drive: Strut your stuff on social media and drive a new Chevrolet for three days.

For the second time this year, General Motors' volume division has contracted with Klout, the service that rates and ranks a person's "social influence," then runs a kind of sampling program for the Web 2.0 era, putting products into the hands of the digital influential. The samples, called "perks," might include software, deodorant, coffee or, in this case, a car.

Chevrolet is paying Klout an undisclosed sum to arrange three-day loans of its new American-made subcompact, the 2012 Sonic, to people with a "Klout score" of at least 35. The program, which began this month and runs through Dec. 14, follows a collaboration earlier this year promoting the Volt, Chevy's $40,000 plug-in electric hybrid. Twenty Klout participants drove the Volt, and all but one posted blogs complimentary to the car, said Cristi Vazquez, a Chevrolet spokesperson in Detroit. The participants also generated about 2,000 tweets, she said.

Ms. Vasquez said that 139 drives would be offered before mid-December in Chicago, New York, Atlanta, Dallas and San Francisco. GM is supplying four or five Sonics in each of the five cities. "It's effective for getting out the message," said Ms. Vasquez. "One of the things we've found is that the best way to get people to change their perception about our company is to get them behind the wheel."

Klout scores range from zero to 100 (though they're hardly scientific) and are intended to measure a person's social influence. Those participating in Chevy's latest program must also have a valid driver's license but are not required to post good things about the products that they test . They can say negative things, or they can say nothing at all.

"We've done about 50 of these partnerships," said Klout CEO Joe Fernandez, who looks for candidates who may have special expertise, for example, in travel or technology. As far as what a Klout deal costs a client, "we don't have a rate card," Mr. Fernandez said, adding that the project with Chevrolet "is less than $100,000."

As more marketers run programs with Klout and its profile rises, it has come under criticism. "Klout has taken a bit of a beating lately," said Steve Rubel, who monitors media and global strategy for Edelman. He referred to a recent story in The New York Times about Klout automatically creating a profile for a 13-year-old, even though the boy hasn't applied for one. Klout says it no longer does this, and now offers members the option to delete their profiles.

The publicity "is a sign of Klout's success, but they have to be careful," Mr. Rubel said. "For Chevy, it's a good play, but they have to make sure that the recipients of their perks disclose that they're received the car for free." That's a key detail because of a Federal Trade Commission guideline requiring bloggers and social-media agents to disclose when writing about products they've gotten for free.

The target demographic for the Sonic campaign skews toward a young, "post-college crowd," Mr. Fernandez said, and represents a push by automakers to mine that vein. It's worth noting, however, that buying power still rests with older consumers and, as J.D. Power reported earlier this year, from 2006 to 2009 the median age of all new-car buyers rose to 55 from 50.

In 2009, Ford took a similar approach with the Fiesta, letting 100 bloggers test -drive the then-new subcompact for six months.

"With the Fiesta, we went to market in a new way," said Andy Prakken, executive director of media planning for Team Detroit. "You need to open the hearts and minds of people. If you just start with advertising head-on, you're probably starting at a disadvantage."

Mr. Prakken contends that the strategy has been successful and that "Fiesta has been a big seller for Ford -- it's bringing younger buyers." Still, Fiesta sales in the U.S. for this past September were 3,967 units, according to Ford. The Honda Civic, traditionally a favorite among entry-level buyers, sold 16,173 cars in September, according to Automotive News data.

Sonic is being marketed by Chevrolet as the fuel-efficient "little brother" of its successful Cruze model. The company, deeply into digital, is funding a social-media contest called "Game of Firsts" that included a giveaway of 10 Sonics.

"This vehicle really needs to keep the momentum going as far as GM's small-car offerings," IHS Automotive analyst Rebecca Lindland told Automotive News recently. It has "to show Wall Street that it can make money on more than just large trucks."