It is one of Australia's oldest and most deep-seated rivalries, more divisive than religion, politics or even football. And it is determined before you're born: depending on your family allegiance, you'll either be Holden or Ford, the only two car brands that count in the suburbs.
It matters not that both companies are American-owned (Holden by General Motors), because for decades their Australian subsidiaries have built models specially designed for the home market: in Holden's case the iconic Commodore, in Ford's case the equally iconic Falcon.
Now the nation – or, to be more precise, half the nation – is in mourning following news that the all-Australian Falcon is to be unceremoniously ditched. The US parent company has decided that it no longer makes economic sense to manufacture different models for different countries. "Those days are gone," Ford's world president and chief executive, Alan Mulally, declared at last week's Detroit Motor Show.
The timing could not be worse for Falcon lovers, preparing to celebrate the big sedan's 50th birthday later this year. Three Facebook sites have been set up by outraged fans, with even Holden supporters urging Ford to save Australia's longest-running model, in the interests of healthy competition.
Nearly every Australian has fond memories of family holidays spent travelling in the roomy Falcon or Commodore. Lovers of the vintage models spend all their free time and thousands of dollars carefully restoring and modifying old bangers.
The Falcon was Australia's fifth-highest-selling car last year, with sales of more than 31,000, compared with nearly 45,000 for the top-selling Commodore. However, all large car models in Australia have suffered from flagging sales in recent years because of higher fuel prices.
There are also fears, which Ford has done nothing to allay, that the Falcon's demise will spell the end of local manufacture. The Falcon has been the mainstay of those operations, with Ford Australia employing nearly 5,000 people at its factories in Victoria.
Mr Mulally declined to reveal whether it was part of the company's long-term strategy to retain the Australian business, which lost $274m (£153m) last year. He said: "Australia is a very important market for us and we've worked hard to be competitive. No matter what, we're going to serve the Australian market."
The first Ford Falcon, the XK sedan, rolled off the assembly line in September 1960. The current model, the seventh-generation FG series, launched two years ago, will not be replaced when production ends in 2015, although industry watchers say the name may survive on locally- badged cars.
Last weekend dozens of Falcon owners staged a protest rally in Queensland, driving in convoy along the picturesque coast road between Cairns and Port Douglas. Organisers pledged to lobby American executives to continue producing the model.
"We'll let them know how strongly we feel about it," said Neil Newcombe, a diehard Falcon fan. "From an Australian point of view, we want to keep [the car] as Australian as we can." Another Ford owner said: "The Falcon is a great Aussie icon. It would be a crime to get rid of it."
Although some Holden fans have been gleeful about the Falcon's passing, others have expressed solidarity. "If they stop making the Falcon, Holden will suffer as well," one warned on Facebook. "We'll have some crap front-wheel-drive thing from the US, so even the Holden fans should show their support."