Rudy Russo, a savvy and ambitious car salesman in Mesa, Arizona, dreams of making it big by running for the state senate. To help him achieve this goal, he works at the struggling New Deal used car lot owned by the elderly Luke Fuchs, who promises to invest $10,000 in Rudy’s campaign under the condition that he keeps the business afloat.
Just across the street, Luke's twin brother and primary rival, Roy L. Fuchs, is desperate to save his own used car lot from being demolished for a new freeway exit. In a bid to cash in on life insurance and force the closure of New Deal, Roy enlists the help of his mechanic, Mickey, a demolition derby driver, to take Luke’s meticulously restored 1957 Chevrolet Bel Air for a reckless joyride—one that ends in catastrophe with Luke as a passenger.
Tragedy strikes when Luke dies of a heart attack shortly after the crash, and Rudy is left with damning evidence that Roy orchestrated the “accident.” Determined to prevent Roy from claiming any inheritance, Rudy teams up with his superstitious coworker Jeff and mechanic Jim to bury Luke on the dealership's backlot, using an old Edsel that once served as New Deal's signature ornament. When Roy comes searching for Luke the next day, Rudy spins a tale that Luke has taken the Edsel on a vacation to Miami.
The chaos continues as Rudy and his crew attempt a live commercial broadcast during a major football game, which descends into hilarity when Jeff’s superstition about red cars causes complications, while a wardrobe malfunction with model Margaret creates a spectacle. Despite the mishaps, the commercial unexpectedly draws a flood of new customers to New Deal. In a particularly creative deal, Jeff deceives a family into buying a station wagon by staging an accident with the lot's mascot dog, Toby.
As Roy employs circus animals to attract customers to his lot, Rudy retaliates by organizing a live stripper show. Luke's estranged daughter, Barbara Jane, returns to the dealership searching for a connection with her father after spending years living in a hippie commune. Rudy, wanting to protect her from the truth about Luke, takes her out on a date and inadvertently convinces her to stay in town.
The rivalry reaches a peak as Rudy’s gang broadcasts another commercial smack in the middle of President Jimmy Carter's address, resulting in the destruction of several of Roy's cars, including his prized Mercedes SL. Furious, Roy attacks Jeff at New Deal, only to unearth the secret of Luke's burial site in the backlot. When Roy returns with the police to dig up the lot, Jim has stealthily moved the Edsel, turned it into a moving tribute, and rigged it to crash into a power transformer, creating an explosive spectacle that convinces everyone of an accidental demise.
As Roy believes he has obtained control of New Deal, Rudy cleverly points out that, with Barbara as Luke’s daughter, she is the new rightful owner. However, when Barbara learns of the deception surrounding her father’s death, she dismisses Rudy, Jeff, and Jim from their positions.
Seeking revenge, Roy cunningly uses his influence at the local television station, KFUK, to edit Barbara's commercial to suggest she has "a mile of cars," simultaneously launching a deceptive charge of false advertising against her. However, fortune smiles on Rudy when he wins a significant bet on a football game, providing him the funds to assist Barbara’s case.
To prevent her prosecution for false advertising, Rudy persuades Barbara to claim she indeed has a mile of cars. To avoid perjury, they must produce more than 250 cars on her lot by 2:45 PM that afternoon. In a race against time, Rudy spends his winnings to buy 250 cars from a Mexican dealer Manuel and arranges for 250 student drivers to deliver them swiftly to New Deal.
Amid Roy's attempts to thwart their plans and Jeff’s lingering fears about red cars, the convoy arrives just in the nick of time. The collective length of the cars measures a mile, saving both Barbara and the dealership. With the impending freeway construction, it is revealed that New Deal will soon be the largest dealership in the state, bringing joy to everyone except Roy. In a moment of triumph and solidarity, Rudy and Barbara share a kiss, solidifying their partnership amidst the chaos.
