Dario Franchitti, Britain’s most successful racing driver, earned a new nickname last week. “Dash Riprock, international playboy,” one of the mechanics from his Target Chip Ganassi team said in a laconic, Deep South drawl, as they crammed on to their tour bus to shelter from a Californian storm. The crew bellow their approval of the new moniker.

At the California Speedway in Fontana, near Los Angeles, this week Franchitti completed his second Nascar series race since leaving the IndyCar circuit, as champion, in a $30 million (about £15.1 million) deal that made him one of Britain’s highest-paid sportsmen or women.

His new crew’s affectionate name for him speaks volumes: Dash Riprock was a TV character in The Beverly Hillbillies, the long-running American series from the Sixties and Seventies. Dash was a Hollywood film star appalled by the rustic Texan family who moved to California after striking oil. “They certainly don’t take any prisoners here. The minute you walk through the door they whack you in the face,” Franchitti said with a laugh over dinner.

He has brought an exotic touch to the sport. His Italian name, rich Scottish brogue – uncorrupted after ten years in the United States – and marriage to Ashley Judd, a renowned film actress, distinguish him in a sport struggling to shed its image as the pursuit of Confederate flag-toting good ol’ boys.

Franchitti raised eyebrows when he chose to quit IndyCars in October 2007 after winning the Indy 500, the Super Bowl of the Indy Racing League (IRL). But stock car racing, despite the Dukes of Hazzard gibes, is the biggest motor sport in the US. Indeed, it is the second most-watched sport in the US, behind American football.

It is not hard to see why: the cars hurtle around tracks, some as short as half a mile, careering into one another at speeds up to 200mph in a hail of sparks. A typical race may have 40 changes of leader. For petrol-addicted Americans, this is the ultimate, and Sky Sports is attempting to introduce it to the British audience.

And Franchitti has caught the bug.

“It’s a totally different thing,” the 34-year-old said. “The IndyCar fans stay in hotels. The Nascar fans love to stay out in motorhomes – maybe half-million dollar motorhomes,” he joked. “They’re having a big party. Normally, I don’t get to see it because I’m driving, but in Talladega recently I got to walk about – it was madness. Tailgate parties, beer, bonfires.”

On the track, the handling of the car and the rough and tumble of the racing make it a different proposition from IndyCars. Enduring the heat generated by a 5.8litre engine over 500 miles is another test. “IndyCars are more demanding and straining, but Nascar races are longer – and they’re hot inside, about 150F [65C],” he said. “It’s like a sauna. The heat builds up and then hits you.” Drivers can lose as much as 12lb during a race.

Franchitti’s finishes, 32nd in both races, do not look impressive, but the experience of Jacques Villeneuve, the former Formula One world champion, indicates how tough it is. The Canadian was dropped by his team after he failed to qualify for the Day-tona 500. “I want to be competitive, that’s the first goal,” Franchitti said. He will hope to emulate Juan Pablo Montoya, his teammate who won the Rookie of the Year award last season after switching from Formula One.

However, Franchitti has found a secret weapon: chocolate bars. “My fridge is full of Irn-Bru and Dairy Milk,” he said. “British confectionaries are extremely difficult to lay hands on across the Atlantic. I’ve got one of the other drivers addicted and I’m feeding his addiction to get information. I just say, ‘Have some chocolate – now how do you take that corner?’ ” The new challenge seems to have rekindled Franchitti’s passion for racing, a love affair that began when he was first put behind the wheel of a go-kart in Bathgate, West Lothian, at the age of 3. He had thought about spending more time with his wife, who is “finishing a film in Canada”, and his friends. “Sometimes I want to say ‘screw it’ – it would be mega to take a year out, visit friends,” he said. “I would love to go and do that, but there aren’t many jobs where you can take a year out, and certainly not in this job.”

Franchitti’s victorious last season in IndyCar racing helped him to walk away from that particular branch of the sport. “I said that, ‘I’m not sure I have the motivation to keep doing this’, so I made up my mind that I wasn’t going to do it again,” he said.

It was a turbulent season. The image of Judd, in a soaked dress, racing down the pitlane to embrace Franchitti at the end of the rain-lashed Indy 500 was splashed across the American press. But he also walked away from two huge, cartwheeling crashes in the space of a week. Both became instant hits on YouTube. “If I hadn’t left IndyCars, I wouldn’t have looked at that second one till I retired,” he said of the crash in Sparta, Kentucky, of which he remembers nothing. However, he does remember the moments before he was sent into the air by Dan Whel-don, a fellow Briton, in Brooklyn, Michigan. “When the car first went into the air, I heard my spotter in my ear saying, ‘Oh s***!’ and I thought, ‘The last thing I’m going to hear in this world is Dave going, “Oh s***!” ’, ” he said.

While he enthuses about Nascar’s safety improvements, he denies that the crashes were part of the reason he left the IRL. “If you’re looking for safety, you don’t race cars,” he said. But Franchitti is aware how lucky he has been. Last weekend he was inducted into the California Speedway’s Hall of Fame – he won the last IndyCar race on the track in 2005. But on the mention of this feat, his earlier ebullience evaporated. “I have a love-hate relationship with this track,” he said, flatly, after a pause.

It was at the California Speedway in 1999 that Greg Moore, the Canadian driver who was his best friend, died in an accident. “It rips it [the racing community] apart, especially for someone as popular as Greg,” Franchitti said. “I lost my best friend that day and I think a lot of people felt like that.” But Franchitti is not one for sentiment and in a moment he was off again, vividly describing the thrill of racing at night. “You could see these floodlights from space,” he said. “I love it – the sparks and the atmosphere are phenomenal.”

Outside the restaurant, the bonhomie continued as, with an almost childlike enthusiasm, he gleefully pointed out and identified the gas-guzzling trucks trundling by. He recently bought a Learjet, but is not nearly as excited by it as he is by his host of cars.

Despite his Hollywood wife and the private jet, Franchitti is ill at ease with life as a celebrity, which is one of the reasons he enjoys returning to relative obscurity in Scotland. He famously once confronted an intruder at his home as he was eating breakfast – an episode that culminated with Franchitti giving chase in his underpants (“This guy had a message from God for Ashley or something,” he said.)

True to form, rather than making the 50-mile trip down the motorway to Los Angeles for postOscars parties after Sunday’s race, he set off in a hire car to drive to the next race in Las Vegas, meeting friends along the way. The pit crew may have to rethink that international playboy nickname.

Sky Sports will show all 38 rounds from the Nascar Sprint Cup series for the next two years. Watch Dario Franchitti live at the UAW Dodge 400 on Sunday from 9.30pm on Sky Sports 2.

What he thinks . . .

Of Lewis Hamilton “I first met Lewis when he had his autograph book as an eight-year-old at the Autosport Awards. I’ve kept a close eye on what he’s doing since. He’s a very gifted driver and he’s always been very determined as well. He’s got what Jackie Stewart calls mind management. He’s as hard as a rock.”

Of not going into Formula One “Things didn’t work out that way and I didn’t make the most of my opportunities. But I have achieved more than I ever dreamt, even though Formula One was what I grew up wanting to do.”

Of the Hamilton-Alonso bust-up “I was always of the opinion that if teammates work together you have a better chance of beating the rest of them. Formula One doesn’t have that mentality. That’s the way it is, has been and always will be.”

Of having a low profile in Britain “I love going home. I can walk down Edinburgh’s main street and the most I’ll get will be somebody saying, ‘Good job, that was great’. Luckily I’m not in the same position as Lewis [Hamilton].”