In Pixar's Cars, the fictional Piston Cup is primarily based on NASCAR.
The Piston Cup races use stock-car shapes, oval tracks, pit stops, drafting, and team-based competition that resemble American stock-car racing. Lightning McQueen, The King, and Chick Hicks compete in a championship structure modeled chiefly on NASCAR rather than open-wheel Formula One.
Cars does not present the Piston Cup as an official NASCAR competition. It creates its own fictional sponsors, teams, rules, and trophy while drawing on recognizable features of the real series.
The connection is also reflected in the film's voice cast: real NASCAR figures, including Richard Petty and Darrell Waltrip, contributed voices. The result combines fantasy anthropomorphic vehicles with a recognizable American motorsport setting.