In Pixar's Cars, the Dinoco 400 is the race that produces the three-way Piston Cup finish.
The film begins with the final race of the Piston Cup season at the Los Angeles International Speedway. Lightning McQueen, The King, and Chick Hicks are involved in the dramatic ending. A tire failure leaves The King out of contention, while Lightning and Chick cross the line in a tie for the championship lead.
Because the result cannot settle the season, a tiebreaking race is scheduled in California. The opening race is called the Dinoco 400, named for the fictional Dinoco racing and fuel brand. Dinoco is also connected to The King's long association with the championship and to the sponsorship prize Lightning wants.
The Dinoco 400 is sometimes confused with the later tiebreaker at the Los Angeles track. The film's plot distinguishes the season-ending race from the final contest that brings Lightning to Radiator Springs.