In Pixar's Cars, the fictional Piston Cup is a family-friendly fictionalization of NASCAR stock-car racing.
The first Cars film follows Lightning McQueen as he competes for the Piston Cup, a championship presented through oval-track racing, sponsor liveries, pit crews, and a points-based season. Those elements strongly mirror NASCAR, the major American stock-car racing organization that helped inspire the film's racing world.
Cars does not use the NASCAR name as the identity of its fictional championship. Instead, Pixar created the Piston Cup and invented racers, teams, sponsors, and tracks for the story. This distinction matters because the movie is an animated setting rather than a documentary account of a real season.
The film includes voices and appearances connected with real motorsport, including racing personalities and commentators. Its racing scenes also draw on recognizable stock-car conventions. Formula One and IndyCar are different disciplines, with different car designs, circuits, and racing traditions, so they are not the best match for the Piston Cup.