Abstract: A decorative radiator cap cover retention system provides for removable attachment of a radiator cap cover to a radiator cap using a retaining ring inside the radiator cap cover to removably attach the cap cover to the radiator cap. The inside of the radiator cap cover may have indentions conforming to the shape of the radiator cap and a groove for the retaining ring. Preferably, the number and shape of the intentions is sufficient to match the shape of many radiator caps.