In Pixar's Cars, what fictional championship do the racers compete for?

In Pixar's Cars, the racers compete for the fictional Piston Cup championship.

The Piston Cup season drives the film's central plot. Lightning McQueen, Chick Hicks, and The King finish the season tied for first, forcing a tiebreaker race at the Los Angeles International Speedway. McQueen's journey to that race is interrupted when he becomes stranded in Radiator Springs.

The Piston Cup is an invented championship, though its oval-track racing presentation draws on American stock-car traditions. It is not the same competition as the World Grand Prix in Cars 2, which is an international event created for the sequel. The cup's name also supports the series' use of mechanical vocabulary for familiar sports concepts.