In Pixar's Cars, what race is Lightning McQueen trying to win at the start of the film?

Lightning McQueen is trying to win the Piston Cup at the start of Pixar's Cars.

The Piston Cup is the championship trophy at stake in the film's final race. Lightning, veteran racer Strip “The King” Weathers, and Chick Hicks finish the season tied, forcing a three-car tiebreaker race at the Los Angeles International Speedway.

Lightning's pursuit of the cup drives the opening conflict. He refuses to share his transport truck with the other finalists, becomes separated from Mack, and ends up in Radiator Springs. His time in the town changes his priorities before the championship race resumes.

The Piston Cup is a fictional competition, but its presentation draws on American stock-car racing and NASCAR traditions. The Dinoco 400 is the name of the tiebreaker race, not the trophy itself. That distinction makes “Piston Cup” the precise answer to the question.