The voice isn't speaking in the hushed, chamber-music tones familiar to National Public Radio listeners. "Though your relatives wouldn't approve, you are in fact listening to us, Click and Clack, the Tappet Brothers," the voice cackles happily over the airwaves. "Don't touch that dial or your dipstick will fall out!" A chorus of ha-ha-has follows, then the strains of hoedown banjo music.

That's Car Talk you're listening to, National Public Radio's call-in show for auto owners in need of advice, sympathy or simply a laugh. The Tappet Brothers—in real life, Tom and Ray Magliozzi—will supply all three during the hour to come. In a weekly program reaching an estimated 1 million listeners, Tom, 52, and Ray, 40, field questions dealing with everything from engine noise to bumper rust. There is no script; every line is off-the-cuff, and many are off-the-wall. Almost all are right on target.

A woman named Joanne phones about a Pontiac that makes a roaring noise. She had taken the car to several mechanics, but they couldn't find the problem.

Ray: "I'm gonna make the noise for you. Woooooooo."

Joanne says that's the noise.

Ray: "It's a bad front-wheel bearing. But let's not assume it's in the front. Noises can fool you. It can easily be the rear-wheel bearing as well."

A woman named Bertha complains about a year-old Toyota "with a lot of noise coming from the back."

Tom: "You got any kids?"

"No, not that small," says Bertha.

"What about your neighbors?

Are any of them missing kids?" Tom persists. Ray: "You should replace the tires. And you may discover you miss the noise. Don't throw those old tires away."

Despite their lube-pit humor and street-cabbie manner, the brothers Magliozzi (pronounced Maliotzee) aren't ordinary grease monkeys, and both pack rather serious degrees from MIT. Sons of a businessman who owned a heating-oil firm, they got interested in cars while growing up in East Cambridge, Mass. Ray liked to pester his older brother as Tom tinkered and fiddled with the countless jalopies he bought. "He was always rebuilding them out in front of the house," says Ray. "I'd always be saying, 'Why are you doin' that?' So I learned, and we learned together."

Tom eventually attended MIT on scholarship, graduating in 1958 with degrees in chemical engineering and economics. He spent 12 years with a company that made instruments for chemical plants, but he wearied of life behind a desk and quit. Ray, meanwhile, was earning his own MIT diploma in the humanities and science before beginning a one-year teaching stint at a Vermont junior high school. By 1973 he, too, wanted a change and moved back to Cambridge, where he joined up with Tom in an auto-repair business.

They founded Hacker's Heaven, a place where do-it-yourselfers could pay by the hour to use the shop's tools and equipment. Two years later Hacker's Heaven evolved into a full-service repair shop renamed the Good News Garage.

When WBUR-FM, National Public Radio's Boston outlet, invited several local mechanics to an on-air panel discussion about car repairs in 1976, Tom Magliozzi was the only one who showed up. His straight answers and quick humor earned him a second invitation, and when he brought his brother along, Car Talk was born. After 11 years as a local radio fixture, the show went national in 1987 as part of NPR's Weekend Edition, then later that same year was given its own time slot and offered to National Public Radio's over 300 member stations. More than 200 accepted.

The hosts decided "very early on that we didn't want the show to be for motor-heads, the people who read Car and Driver in the bathroom," says Ray. They prize utility over pizzazz, admit to a prejudice in favor of big American cars ("Imperial Star Cruisers") and often look beyond the tool rack for answers. When a caller named Jack insists he needs a four-wheel-drive vehicle for an upcoming highway trip—and rejects the idea of renting one—Tom quickly spots the problem. "When was your 40th birthday?" he asks, laughing. "Two years ago?"

Jack: "Four."

Tom: "You've got a lot of suppressed desires, so I guess you've got to do it. For you, get the biggest one you can find."

Later, when the call is done, Jack marvels at the brothers' wisdom. "They're very perceptive," he says. "They knew they were talking to someone in the throes of a mid-life crisis."

Such praise hasn't changed the Magliozzis or their tastes. Tom proudly tools around in a '74 Chevy convertible whose top seldom works and whose radio never plays. Ray drives an '87 Dodge pickup. "People shouldn't take their cars so seriously," he says. "It's not brain surgery."

There are, of course, exceptions. When a caller tells the brothers about overinflating his tires to stop their squeal, their voices turn somber. "This is serious, this is no joke," Tom tells the caller. "Don't be a fathead. Don't be a cheapskate. You're gonna get killed."

These days, Ray runs the garage with the help of four mechanics, Tom having left the business in 1980 to return to academia. The latter has since accumulated two M.B.A.s and a Ph.D. in marketing, a subject he teaches twice a week at Boston University. Both live in modest suburban homes outside Boston, Tom with his second wife, Joanne, and two children (he has a grown daughter from an earlier marriage), Ray with his wife, Monique, and their two kids. In their off-hours, the brothers have been working on a layman's car-repair book, due later this year. And starting this month they'll put their advice into a syndicated newspaper column.

Meanwhile, car owners who like to talk about their troubles wait for Sundays, when the brothers head for their tiny studio at Boston University's School of Communications building to start fielding calls and answering mail. They already receive 750 letters each week, and the pile is growing. Car Talk "is the most popular new program we've added in the past year or two," says Ken Davis, program director of WBEZ in Chicago. Says Mike Flaster, program director of KPBS in San Diego: "We're predominantly a classical music station. [But] they're literate and funny, sort of Zen and (he Art of Motorcycle Maintenance comes to radio."

Even for NPR's highbrow listeners, the mix has proved as potent as high-test octane. Says Tom: "Some guy I met said it's amazing how we use cars on our show as an excuse to discuss everything in the world—energy, psychology, behavior, love, money, economics and finance. The cars themselves are boring as hell."

—Amy Schulman in Cambridge