Car gaskets and seals are designed to prevent the fuel and air mixture from leaving the cylinder during combustion, while also keeping oil from leaving the crankcase at the same time. In older engines, you may find that your gaskets are made of cork, but in newer vehicles it is likely that they are made of thin metal or carbon. Most seals are made out of rubber and are placed between the rotating engine parts. While it is important that these are replaced when a leak in the engine is detected, it is just as important to replace the gaskets and seals when any corresponding components of the engine are replaced.