Rubber grommets are most commonly used in cars to reinforce holes made in a material in order to pass electrical wires, mechanical linkages, hoses, heating and cooling ducts, and other items through the material. Rubber grommets are often used in cars when passing these types of items through the car's firewall, which divides the vehicle's engine compartment from the interior cabin.
Rubber grommets are sometimes use to seal filler neck assemblies such as those found on the vehicle's windshield wiper housings. Rubber grommets are also used in cars as valve covers or as part of the vehicle's antenna assembly. When rubber grommets are used in a car's engine compartment, they are designed to withstand temperature fluctuations that may occur due to engine heating. Rubber grommets can also be used to help prevent leaks and improve the seal of components in and around the car's carburetor. When used in this application, rubber grommets help reduce friction that causes metallic parts to warp and ultimately break down.
Rubber grommets also serve as insulators for hoses and wires running to and from the car's carburetor and other engine parts. This usage helps maintain a consistent temperature in and around the carburetor, which reduces breakdown due to wear and tear.