Roger Penske, owner of the second-largest U.S. auto retailer, has emerged as another potential bidder for General Motors Corp. (GM)'s struggling Saturn brand, people familiar with the situation said.

Penske owns Bloomfield Hills, Mich.-based Penske Automotive Group Inc. (PAG), which operates 156 franchises in the U.S. and 148 internationally. A Penske spokesman declined to comment on any interest in Saturn.

News of Penske's interest comes as GM on Monday hired veteran auto industry advisor Steven Girsky to help sell the Saturn brand by the end of the year.

GM is racing to offload the brand and its dealers as the company tries to avoid being forced into bankruptcy protection alongside Chrysler LLC. The auto maker has until June 1 to convince the Obama administration it can survive outside Chapter 11.

GM said Monday it is reviewing "expressions of interest" from "a number" of potential buyers. Under any Saturn deal, GM would eventually stop providing the vehicles and they would be built by another manufacturer and sold through the Saturn retail chain.

Girsky, a former Morgan Stanley analyst and one-time advisor to departed Chief Executive Rick Wagoner, will help GM evaluate the offers.

GM stock closed flat on Monday, at $1.81 per share. Penske shares finished 1.3% higher at $13.56.

Penske, a billionaire with deep Detroit ties, also has experience developing other brands. His company is the exclusive U.S. distributor of the Smart car produced by Daimler AG. (DAI).

He owns auto-racing team Penske Racing and, recently, he chaired the Detroit Super Bowl XL host committee and brought the game to the Motor City after raising $12 million for the event.

Penske joins at least one other suitor.

A group that includes Oklahoma City-based private equity firm Black Oak Partners LLC came forward last month as potential buyers. A GM spokesman said Monday the company is considering the offer.

The Black Oak group proposed a plan in which it would seek to transform Saturn into a fuel-efficient brand, sell GM vehicles through Saturn's network of U.S. and Canadian dealers, and later add vehicles from other auto makers.

John Pappanastos, who is leading Saturn negotiations for Black Oak, said he is certain the brand will have a buyer

"It's a viable opportunity in this market," Pappanastos said of Saturn. "It will be a low-cost entry point for an auto maker who wants to get into the U.S."

Saturn has lost money since GM launched the brand in 1984 - first marketed as "a different kind of car company" - as a way to fight off competition from foreign competitors, such as Toyota Motor Co. (TM).

Saturn generated much enthusiasm and a reputation for top-notch customer services, but never delivered the competitive edge GM hoped for.

But GM's efforts at reviving the lineup by spending big on fresh vehicles proved insufficient, and the company said it would sell or dismantle Saturn as part of restructuring plans.

The company had hoped to garner interest at least in Saturn's retail network. Saturn dealerships often are newer and more modern than the average GM-brand dealership, and they tend to be stationed in more desirable locales.

-By Sharon Terlep, Dow Jones Newswires; 248-204-5532; sharon.terlep@dowjones.com.

(Jeff Bennett and John Stoll contributed.)