New vehicles

New vehicles may contain flaws or defects in workmanship, caused by design flaws or by an error during the automotive factory build process. These errors can range from parts being installed incorrectly to a tool that was used to build the car not being removed or a batch of materials with structural or chemical flaws. The idiom "Friday afternoon car" was used to describe new cars that had been delivered with numerous faults or suffered from an excessive number of warranty claims early in their lives – based on the premise that assembly line workers were far more likely to make errors at the times when they were perceived to be least interested in the standard of their workmanship.

Consumer protection legislation typically labels vehicles as "lemons" if the same problem recurs despite multiple repair attempts (such as three times in a row over a short period, where previous attempts have not corrected the problem) or where defects have caused a new vehicle to be out of service for a prolonged period (typically 30 days or longer) for repairs.

Lemon laws primarily serve to force manufacturers to buy back defective vehicles or exchange them. Depending on the jurisdiction, a process similar to vehicle title branding may also be used to warn subsequent purchasers of the history of a problem vehicle. While this portion of a vehicle's history is usually not retained with the title when exporting it to another jurisdiction, at least one jurisdiction (California) has started compelling manufacturers to brand the titles of any previously reacquired vehicles that they import or export from the jurisdiction.

US Federal law

The Magnuson–Moss Warranty Act is a United States federal law enacted in 1975 to protect consumers from deceptive warranty practices. The Act was sponsored by Senator Warren G. Magnuson of Washington with co-sponsors Senator Frank Moss of Utah, and U.S. Representative John E. Moss of California. The purpose of the Act was to make product warranties more easily understood and enforceable, and to provide the Federal Trade Commission with a means of better protecting consumers. The Act does not force a manufacturer to include a warranty with its products but if there is one it must be in writing and comply with the rules of the Magnuson-Moss Warranty Act.^[5]

Used vehicles

While used cars may be plagued with the same problems that beset new vehicles, used vehicles may also have been abused, improperly maintained or poorly repaired, been unprofessionally rebuilt after a collision or tampered with in some manner to conceal high mileage, mechanical defects, corrosion or other damage.

One form of lemon is called a cut and shut or clipping, a form of body collision "repair" based on buying a wrecked car and sawing off the wrecked section to replace it with a matching section from another (similar) car. If improperly repaired, these vehicles may be inherently dangerous; at high speeds, or in an accident, the car may come apart due to the weaknesses of the welds or pins connecting the two segments of the vehicle or mismatches of segments.^[6][7] In the UK cut and shut cars are treated like any car that has had major repair work resulting in what is essentially a new car. They must first be inspected for road-worthiness, be assigned a new registration number and pass the standard MOT test. If this is successful, they will be given a "Q" registration, meaning they are a kit, or composite car, and not an original unit from the manufacturer. ^[8] In some states of the USA, the sale of cut and shut vehicles is illegal. Cars created using two or more large sections of previous ones are sometimes called "zipper cars".