General Motors is in the business of making cars. Metro tries to get people out of them.

So when GM ads went up in the subway urging riders to "tear up your monthly pass" and buy an Oldsmobile Aurora, transit officials fumed.

"It's unconscionable that a major car manufacturer would come out with an ad trying to view us as a competitor," said Metro General Manager Lawrence G. Reuter, who noticed the ad while riding an Orange Line train to work one morning.

The Oldsmobile ads show a side view of the Aurora, a sedan designed to compete with models such as Toyota's Lexus GS 300 and Honda's Acura Legend. The Aurora's base price is about $32,000, or roughly 62 years worth of $2 workday round trips on Metro.

Above the picture of the car, one ad says, "Next time, catch the Express." Another says, "Tear up your monthly pass." A third ad, playing on Metro's smoking ban, says, "Feel free to smoke."

Similar ads have run this fall on subway trains in New York, Boston, Chicago and Philadelphia.

"The ad sends an anti-transit message, not a pro-Aurora message," said Metro spokeswoman Patricia A. Lambe. "It doesn't matter what car you're in, it's no 'express' driving in on the Woodrow Wilson Bridge or the Beltway."

Reuter and Jack R. Gilstrap, executive vice president of the American Public Transit Association, told GM officials that the ads targeted one of the few industries that is trying to reduce the environmental damage caused by the auto manufacturer's products.

Nine of 10 Metro riders own and use cars for trips they cannot make on public transportation, transit officials said, which indicates that people choose to take Metro.

"If the millions of daily transit users took your advice literally, both cars and buses would risk being stuck in commuter traffic from dawn to dusk," Gilstrap said in a letter to John F. Smith Jr., GM's president and chief executive.

"There's a better way they could have had fun," Reuter said yesterday.

"I can't dispute what he says," said Gus Buenz, Oldsmobile's public relations director in Detroit. "There are lots of ways to have fun and do advertising without conflicting with someone's basic business."

The Leo Burnett agency of Chicago did the creative work on the ads, while another agency placed them. Metro received $15,120 for displaying them.

The ads went up in October and the campaign ended Wednesday; some of the ads were still on display yesterday.

"We won't stumble again," Buenz said."

Metro is limited in its ability to censor such material because of constitutional protections of free speech. Advertising submitted to the transit agency must be accepted if it meets the guidelines set out in Supreme Court cases.

Metro has been successfully challenged in court for refusing advertising and there are other poster campaigns that probably offend transit officials.

A Washington Post ad campaign that began yesterday on Metro buses pictures a bus driver with an arrow pointing to him. "He'd rather be driving a 1966 Ford Mustang. How about you?" asks the ad, which publicizes a new classified advertising service.

Some transit officials said The Post's ad could be construed as anti-transit. That's not the opinion of a representative of the newspaper.

"We clearly don't see this as anti-transit," said Theodore C. Lutz, The Post's business manager and a former Metro general manager.

"We're trying to influence people to try to think about us when buying a used car."

CAPTION:"The ad sends an anti-transit message, not a pro-Aurora message," said Patricia A. Lambe, of Metro.