Lightning McQueen joins the Rust-eze racing team in Pixar's Cars.
At the beginning of the film, Lightning is a rookie racing for Rust-eze, a sponsor associated with a rusty-medicated-bumper-ointment business. The sponsorship is represented by Rusty and Dusty Rust-eze, who support Lightning during the Piston Cup season. Their branding remains one of the most recognizable commercial elements in the Cars world.
Lightning initially dislikes the Rust-eze image and dreams of replacing it with Dinoco, the prestigious sponsor associated with The King. After Lightning learns humility in Radiator Springs, Rust-eze remains connected to his career, and the relationship develops across the trilogy.
Dinoco is a separate sponsor, not Lightning's original team. RPM and Octane Gain are other fictional racing brands visible in the films. The wording “joins” refers to Lightning's sponsored racing identity in Cars, rather than a later change in ownership or paint scheme.