When Tim Robbins and his wife Susan Sarandon left the Vanity Fair Oscar party last March in something that was patently not a Hummer, the colossal faux-military vehicle popularised by Governor Arnold Schwarzenegger and a symbol of road-hogging prowess, all of Los Angeles let out a knowing sigh.
Not for the first time in their lives, Robbins and Sarandon were making a political statement. (Or, in this instance, an environmental one.) Their choice of wheels these days is a Toyota Prius. Styled like a wedge of Wisconsin cheese, this car is no beauty, nor has it won any prizes for guts or acceleration. But it has something very special beneath its bonnet: two engines.
The Prius is among those new hybrid cars that give its owner a mode of transport, and a reason to be smug. With an electric motor that kicks in to do the work of the regular petrol engine at slower speeds, it gives fabulous miles to the gallon and pollutes less too.
So, the Robbins-Sarandon family was taking up arms in a very Hollywood cultural war. On the other side of the battlefield were Arnie - he was the first American to buy a Hummer when it first came out 10years ago - and the brigades of other more recent converts to the General Motors-owned brand, for whom taking to the road is about flashing muscle. The really pumped-up like to ride in a stretch Hummer.
The Hummer and its recent variant, the H2, represent the apotheosis of America's long-running love affair with cars-on-steroids. In the 1950s, it would have been an obscenely long power-steered saloon with tail fins and a drive that was about as firm as a Krispy Kreme doughnut soaked in milk. But since the mid-1990s, the highways from Connecticut to Colorado have been invaded by so-called SUV's, or sports utility vehicles. Jeeps became Explorers became Expeditions became Navigators. I am bigger than you; get out of my way.
Not so fast. Americans are beginning to question whether the love affair with big is sustainable. The reason is clear. The price of petrol here is scraping record highs, touching an average of $2 (£1.12) a gallon nationwide, compared to $1.50 a few months ago. This may be still far below what Europeans are used to (though an American gallon is smaller than the imperial nephew) and it still cheaper than a gallon of milk. But still, drivers are starting to wonder.
Arnie, you are going out of fashion. For symptoms, look no further than the sudden slump in Hummer sales figures. After the launch two years ago of the H2 - which looks even more like a giant Dinky Toy than its predecessor - General Motors struggled to keep up with demand. It was the only brand on its books that it never had to push with rebates and discounts.
Since the start of this year, that has changed. Hummers are suddenly being stranded on the showroom lot. And what is the most common complaint of those already driving a Hummer? Its absurdly low mileage of about 11 miles per gallon. "I don't know what it is," said Jim Lynch, a dealer building a new garage for his Hummers in a suburb of St Louis, Missouri. Across the US, Hummer sales were down a shocking 25 per cent in April and Mr Lynch is struggling to shift his inventory. "I know in some parts of the country it became the poster child for large SUVs for people who didn't like them. I know they're burning them in California." (Not quite, but one Hummer garage was hit by an arson attack last year.)
Perhaps even more worrying for Detroit, still the capital of the American car industry, is a similar slowdown in recent months of sales of other over-sized family vehicles. General Motors this week has temporarily closed an Oklahoma factory that makes some of its SUV models, because of a supply glut. It hopes to crank up the production lines again next week. Ford admits its numbers are also down this year for its largest SUV models, the Expedition and the Tarmac-thumping Lincoln Navigator.
So here is the news from Detroit, and it should not surprise you. The Big Three - GM, Daimler-Chrysler and Ford - are rushing to join the hybrid revolution. What is a bit surprising is that they seem to be finding a way to combine hybrid technology with the American taste for size. No longer do hybrid cars have to be either weird-looking, like the products of science experiments, or particularly small.
First off the blocks this autumn - and already earning rave reviews from the car-magazine editors - is the new hybrid version of the Ford Escape. This is an SUV, albeit a fairly modest member of that family. With the Prius, it will be only one of two cars on the US market that are fully hybrid. In other words, there will be times when you are at its wheel when the petrol engine will cut out and nearly all noise from beneath the bonnet will cease when the electric motor takes over.
That might brings some concerns for pedestrians and cyclists unable to hear the roar of oncoming traffic, but more stealthy wagons are on the way. Honda is rushing out a hybrid Accord. Most impressive of all is Toyota's new addition to its line of luxury cars bearing the Lexus name. Available in the US next year will be a hybrid sister to its fast-selling and highly stylish Lexis SUV.
Not a hybrid but part of the same trend is a soon-to-be released diesel-drinking version of the Jeep Liberty. With its V6 engine, it will consume 25 per cent less fuel than the regular Jeep Liberty. In January, a senior executive at General Motors suggested hybrid cars were an "interesting curiosity" but nothing more.
Already, the company has changed its tune. It has no hybrids in its showrooms now, but it is supplying hybrid trucks to some municipal government fleets, for instance in Miami. And it has sold hybrid buses to Seattle. More importantly, it is promising to be ready to make a million hybrid versions of its most popular models as soon as in 2007. (Americans buy about 17 million new vehicles a year.)
Curiously, the economics of buying one of these hybrids is not as attractive as it seems at first sight. The mileage statistics pasted on these new cars are often misleading. In the case of the Prius, testing by the federal Environmental Protection Agency, EPA, shows it can run for 55 miles on a single gallon of petrol. But the test the EPA uses is widely acknowledged as being skewed. Other tests have shown the Prius manages 43 miles per gallon.
Bear in mind also, that hybrid cars are generally more expensive. A car that costs about $20,000 will sell at a premium of $2,500 more if it has the twin-engine technology. You would need to drive an average of 15,000 miles a year to make that money back at the pump.
For that reason, many motoring experts say if petrol reaches $4 a gallon there may be widespread defection of Americans from their traditional petrol-only cars. But interest in hybrids is picking up. Toyota reports that it has an orders backlog today of about 20,000 Prius cars, and that sales of the model this year are likely to be up by 50 per cent to 50,000 units.
"It's way too early to write obituaries for big American vehicles," the chief motoring correspondent for the Detroit News newspaper, Daniel Howes, wrote in his column yesterday. But he added: "The success of the Toyota's Prius - and Ford's eagerness to get the hybrid Escape in driveways - suggests we're beyond the point of hybrids-as-fad".
So never mind if buyers of these news cars may not save much money. Whether it is Iraq or the soaring price of fuel or some kind of reaction against runaway consumerism, there is a growing sense hybrids are the new cool in America's showrooms. It is planet-conscious against Planet Hollywood, tree-hugging versus tree-chopping. It may even be Democrat versus Republican.
Wes Brown, who is an analyst at Iceology, a Los Angeles market research company, said: "We look at the higher-end SUVs as really being fashion statements. It had its moment in the sun when everyone had to have one. And now, that's it. It's done."
But if you can soon have a hybrid Lexus SUV, who is to say a hybrid Hummer is not around the corner? But that would seem to deny the Hummer ethos: consume for the sake of consumption.
'People stared at my new car. I call it Prius envy'
I'd like to say I drive the trendiest car in southern California, but by now - with oil prices rising, geopolitical angst over the Middle East soaring, and the rebellion against gas-guzzling monster four-wheel drives in full swing - there are just too many of us on the roads to feel that special any more.
Fifteen months ago, when I first got my hybrid petrol-electric Toyota Prius, people stopped and stared. They wanted to jump in for a spin, wanted to experience that strange sensation of noiselessness at intersections, wanted to look at the complex engine diagrams and minute-by-minute fuel-efficiency charts on the fancy dashboard monitors.
Prius envy, I called it. People felt compelled to go out and buy one of their own, or else to offer up excuses why, much as they'd like to, it wasn't quite for them.
People ask how long I had to wait for one. (I didn't; I just strolled into a Toyota dealership and there it was.) They ask if it was horribly expensive. (It wasn't; it cost less than my previous car, and I get a tax break too.)
They gasp when I tell them that after 100 miles the gauge still says I have a full tank. Best of all, they look at me with new-found admiration, as if to say: "Maybe you're not such a loser after all."
The Prius is also fun to drive. A computer screen shows which engine is working when and offers graphics plotting your exact fuel efficiency in five-minute chunks. Under about 10mph, the motor engine cuts out altogether, a bizarre sensation that makes you think at first that you've stalled, and then that you are driving a milk-cart.
In an America that is as polarised about car fashions as it is about politics, the growing cultural divide is all too visible on the streets. On the one hand, the Hummers, Navigators and Expeditions - so vast and intimidating they look like they would eat a Prius for breakfast. And, on the other, our fuel-efficient, ultra-low emission hybrids.
Until recently the fuel efficiency message has found little favour across much of America, where wanton petrol consumption is a badge of pride (but that is changing now that fuel prices have rocketed).
But in California, which has always set the pace on environmental car regulation, the battle for the future is in full swing.
In this harsh world of sharks versus minnows, I know which side I'm on, and it's not just because of the lower fuel bills. (I get 40-45 miles per gallon, compared with less than 20 for most Sports Utility Vehicles, or SUVs, as they are known here.) I have terrific manoeuvrability, which means I can be in and out of parking spaces in the time an SUV takes just to back up for a turn.
Diane Binder, an LA mother married to a television actor and producer, recently sold her SUV and bought a hybrid after finding a protest sticker on her car that read: "I'm changing the environment - ask me how."
Ms Binder told me: "My thinking was heading in that direction anyway, but the sticker spurred me into action. There is no justification for polluting the planet with huge vehicles we don't need."
Although the Prius looks small, it fits five people comfortably. Boot space is a bit tight, but the new 2004 model has made significant improvements in that department.
The Prius costs only modestly more than other cars of its size, and there's a nice government tax break to ease the pain. What's not to like?