Used car salesman Rudy Russo (Russell) needs money to run for State Senate, so he approaches his boss Luke (Warden). Luke agrees to front him the $10,000 he needs, but then encounters an "accident" orchestrated by his brother Roy (also played by Warden), who runs the car lot across the street. Roy is hoping to claim title to his brother's property because Roy's paying off the mayor to put the new interstate through the area. After Luke disappears, it's all out war between the competing car shops, and no nasty trick is off limits as Rudy and his gang fight to keep Roy from taking Luke's property. Then Luke's daughter shows up.
Tropes used in Used Cars include:
- Black-and-Gray Morality: Rudy and his boss are not saints when it comes to selling cars, and Rudy was going to start his road in politics with a bribe, but Roy has no problem doing murder and framing people for an alleged crime.
- Cain and Abel: Neither Fuchs brother is a saint, but Roy isn't adverse to murdering his sibling and manipulating the system to get what he wants.
- Cash Lure: Rudy uses a $10 bill on a fishing line to attract a customer from across the street at a competing car dealer. When the customer is chasing the money and not looking at traffic, Hilarity Ensues.
- Chekhov's Armory: In the beginning of the film, a Mexican guy who supplies them with cars says he has a ton of them just sitting around (there has to be at least 250 in a picture he shows them). Later in the movie a driver's ed teacher, who they sold crappy cars to, is angry because now his 250 students can't learn to drive. At the end of the movie the lot is being sued for false advertisement (due to the bad guy messing with an ad to say they have a mile of cars then paying off "experts" to say it wasn't tampered with). A mile of cars is said to be about 250 cars and if they don't have that many at the lot when the judge comes by to see they lose. Remember how the Mexican had at least 250 cars and how the teacher had 250 students?
- Exact Words: The entire third act revolves around Roy Fuchs placing Rudy and his coworkers in legal trouble for the alleged false advertisement of not owning a literal mile's long worth of cars in their lot (a promise that exists only because Roy doctored the ad video). Even after they manage, through various insane (and probably illegal on their own) means, to get enough cars to measure 99.9% of a mile to the lot, Judge H. H. Harrison is seconds away from ordering Rudy's arrest when a lucky break happens that makes a car measure the five inches that were missing.
- Handcuffed Briefcase: Rudy is in the process of buying his way into state government and gives a Corrupt Corporate Executive a bribe in a briefcase, which the executive handcuffs to himself while they're both sitting in a limo. When Rudy decides to renege on the deal and use the money for (slightly) more noble purposes he grabs the briefcase and slams the car door on the chain on his way out, breaking it.
- Hanging Judge: Judge H. H. Harrison is portrayed as a hanging judge, complete with model guillotine and hangman's noose on his bench. The film's villains take a chance on using Harrison, an honest judge, simply because he's guaranteed to give the harshest sentence should he find the heroes guilty (why not go for a corrupt judge that could do the same is only answerable with "because it wouldn't be as funny"). Sure enough, when Rudy manages to get enough cars to measure just five inches short of a literal mile, Harrison starts to order his arrest because it's still not a mile's worth when Rudy bangs on the car in frustration, making the license plate (which covers the fuel cap) to accidentally drop down and extend the bumper the necessary number of inches.
- Heh Heh, You Said "X": The car dealership is doing an illegal broadcast by tapping into a football game and substituting their own commercial for the video feed. One of the car dealers has a deathly fear of red painted cars, and when they cut in the commercial and the flood lights are turned on, he realizes it's not a dark blue car, but a red one, so he says, "What the fuck is this, Rudy, a red car?" One of the technicians that arranged for the illegal tap in turns to Rudy and says, "Did he say 'fuck'? That's an FCC violation!" As if what they're already doing isn't...
- Honest John's Dealership: The entire film is a war between two such dealerships.
- Kitschy Local Commercial: First they hijack a TV transmission of a speech from President Carter to hawk their rival's cars (thus getting him into trouble). In another live commercial their model loses her dress. Later a legitimate (bad) commercial says that they have "styles" of cars but the audio is altered by people working for the rival to say "miles" instead; the lot is then sued for false advertising, since they don't have a mile of cars.
- Of Corpse He's Alive: Luke is purposely given a fatal heart attack during an extreme test drive. The body is disposed of by propping the dead guy up in his favorite vintage car, setting the car in drive, and having it crash while a big sale is going on at the first dealership. The dead guy is subsequently buried in his car.
- Recorded Spliced Conversation: The climax happens because the rival dealerships splices and edits the commercial in way that will give their false advertisement complaint a leg to stand on.
- Shoot the Television: Roy L. Fuchs smashes his TV set in a rage during President Carter's televised address, after the broadcast is hijacked by the employees of his brother Luke's used car lot, who were seeking to "advertise" their rival business on TV and destroy several cars on Roy L.'s lot in the process.
- Stripping Snag: A woman in a live TV advert gets her dress caught on a car's hood ornament and (surprise) has it completely yanked off when the hood pops open.