In Pixar's Cars, Rust-eze is printed on Lightning McQueen's race car as his fictional sponsor.
Rust-eze is an automobile-buffing product company whose sponsorship helps McQueen enter the Piston Cup season. The brand is represented by Rusty and Dusty Rust-eze, who bring McQueen to the racing world and later help connect him with the Dinoco opportunity.
The sponsor is important to McQueen's character arc because he initially sees Rust-eze as embarrassing and wants the more prestigious Dinoco sponsorship. By the end of the film, he has developed loyalty to the people who supported him before he became famous.
Dinoco is a separate fictional sponsor associated with The King and later with racing opportunities. Piston Cup is the championship, not a sponsor, while Octane Gain is another fictional racing brand.