Dinoco is a fictional racing sponsor that appears prominently in Pixar's Cars.
The blue Dinoco brand is associated with the Piston Cup and with The King, a veteran racer driving the number 43 car. Its sponsorship represents prestige and success within the film's racing world. Lightning McQueen becomes especially interested in Dinoco because winning the Piston Cup could lead to a coveted Dinoco sponsorship.
Rust-eze is another important sponsor in the story, but it is not the same brand. Rust-eze sponsors Lightning McQueen at the beginning of the film, while Dinoco is the larger, more prestigious opportunity he hopes to secure. This difference is a common source of confusion.
Dinoco also appears elsewhere in Pixar's universe. The company is visible in Toy Story as a gas station and is treated as a recurring fictional brand, linking Cars to Pixar's broader tradition of small visual references.