In Pixar's Cars, Lightning McQueen races for the Rust-eze sponsor.
Rust-eze is presented as a medicated bumper ointment company, and its branding covers Lightning's red body with yellow lettering and lightning-bolt graphics. At the beginning of the film, Lightning dislikes the sponsor and dreams of moving to the prestigious Dinoco team.
His attitude changes after the events in Radiator Springs. Rust-eze's owners, Rusty and Dusty Rust-eze, supported him before he became famous, while Dinoco represents the glamorous reward he thinks he needs. The contrast helps the film explore loyalty, gratitude, and the difference between fame and genuine friendship.
Dinoco is a common answer to this question because it is closely connected with the Piston Cup and the film's final race. However, Dinoco is not Lightning's original sponsor; Rust-eze is the sponsor shown on his car.