Mary from Georgia has a problem. Her husband doesn't listen to her. They have the same argument again and again. And she's afraid the relationship might come to a violent end. Clearly Mary needs advice. But she skips the therapist and doesn't even bother with an agony aunt. Instead Mary calls one of America's most popular public radio shows: Car Talk.

Tom and Ray Magliozzi have spent the last 22 years doling out advice about cars over the radio. The brothers from Massachusetts answer just about any question, from the technical (How do you fit a V6 engine into a 1982 Chevette?) to the silly (Is it okay to use the restroom at McDonald's while on a road trip without buying anything?)

Every week two million people tune into Car Talk on the 480 stations that carry the show. Ray, who like his brother can't resist a corny joke, says the reason the show has such popularity is that cars are 'just a vehicle' to talk about other things. They particularly like giving out relationship advice...

Mary: I need some marriage counselling here on a car problem.

Tom: Oh, excellent. The husband is right. Get off the phone. What are you wasting our time for? Mary: Right, right. So, I know that ya'll are going to take my side on this.

Tom: Well, we might.

Mary: Okay. My husband goes to the gas station and we're all in the car and he gets out of the car and, in order to keep the air conditioning running, he pumps the gas while the car is running. And I told him to turn the engine off.

And he says: 'Have you ever heard of anybody blowing up while they're pumping gas in the car?' And I say 'No, because everybody else turns the engine off.'

Ray: And he's the only dope that doesn't.

Mary: Right. He said he would abide by what you guys say...

Tom and Ray champion her cause, cautioning that if the car does blow up, her husband wouldn't be able to run fast enough to get away. 'Well,' says Ray, 'he might run that fast if his butt were on fire!'

They often side with women, and many women listen to and call the show. In New York, more women listen than men. 'I think we attract women callers because we don't berate them for not knowing anything,' says Ray. Tom adds: 'We've always said guys are harder to deal with because, either they think they know something about cars, or they think they ought to sound like they know something. Whereas women are more than happy to say they know nothing. And we say, 'Neither do we."

The show's even popular with people who don't drive; in fact, a third of Car Talk listeners in New York don't own cars. Part of the reason for its popularity, says Torey Malatia - general manager at WBEZ in Chicago where Car Talk is the most popular single hour of programming - is that it's just plain funny. 'It's particularly potent on public radio. Public radio in the US is fundamentally humourless,' said Malatia. Car Talk is 'sort of like putting a splash of pink in an otherwise black room.'

Nobody enjoys Tom and Ray's jokes as much as Tom and Ray do. They often have to stop talking because they are choked by howls of laughter at something they just said. 'They are off the air what they are on the air,' says Dean Cappello, vice president of programming and operations for WNYC radio in New York.

'There's no pretence. They're not actors. There's no fru fru.' On the show, on their website, in their twice-weekly syndicated column which appears in, among others, the Washington Post, the Dallas Morning News and the Boston Herald, they are never afraid to speak their minds. And as the following show, there's little they don't have an opinion on...

• Peugeots and the French Caller: The car does not start when the engine gets warm. You wait a good 20 minutes, and it eventually will cool down and then it will start.

Tom: It may sound like a technical problem. But the fact is that it is a cultural problem. All Peugeots do this. But in France people drink a lot more coffee. They sit around in little coffee shops, so no one would ever shut off an engine and come back to it in less than 20 minutes. So no one in France even knows that Peugeots do this because, during that 20-minute period, they are sitting in a little bistro or a sidewalk cafe. They are drinking cafe au lait and smoking cigarettes. They come back and every single Peugeot starts right up.

• Hopeless British cars

Ray: Brits fell out of love with their cars because they didn't run for shit.

Tom: I've owned a couple of British cars.

Ray: Notice he didn't say: 'I've driven a couple of them.' He's owned a couple. All I can say is thank God the Japanese make cars whose steering wheels are on the same side as British cars. Otherwise the Brits would be doomed to driving their own cars.

• The stupid letter R

Caller from Australia: I feel comfortable with you guys [they have New England accents] because you don't say your Rs either.

Ray: An R is a stupid letter.

Tom: Totally unnecessary.

Ray: Except at the beginning of a word. So you don't say Obert instead of Robert. That's okay. But otherwise it's completely unnecessary.

They poke fun at their callers, and anything else they can think of - and they are their own favourite targets. Both have lived most of their lives in and around Boston. Tom, 60, led an unsettled life for years, working a range of jobs: house-painter, army cook, college professor. He has a heavy beard and unkempt hair, and a tendency to rant about his favourite social issues on the air.

Ray, 12 years younger, started out as a teacher. In the early 70s, he convinced Tom to open a garage with him.

Their show first aired on a Boston public radio station in 1977. In the early days, it was much more technical, with Tom and Ray fielding questions from grease monkeys who stood over their car engines as they talked. Since Car Talk was syndicated nationally in 1987, it has become less technical and more whimsical. Even after 22 years they still sound like they are having a good time. And they can't resist giving themselves one last kick in the pants as they sign out every week.

Ray: Well, you've squandered another perfectly good hour listening to Car Talk. Thanks so much for listening and remember, don't drive like my brother.

Tom: Don't drive like my brother.