DIN
Why is mechanical seal important in this situation? It is because the rotating shaft has to move in a wet environment, but there should not be the leakage of pressurized fluid. Hence, the role of a seal is quite critical.
Selecting Quality Rubber Valve Cover Gaskets
There are four general motor oil types:
If you find a gap, measure it by sliding a feeler gauge under the ruler.

If you follow the above instructions, the oil seals should work properly. Also watch the video below for an example of the installation process.
Carefully lift off the cover. If it sticks, gently tap it sideways with a soft-faced rawhide or nylon hammer, or with the heel of your hand.
The valve cover gasket plays a critical role in maintaining the integrity of the engine by preventing oil leaks and maintaining proper lubrication. It ensures that the engine remains free from oil leaks, contributing to its overall efficiency and reliability. A high-quality valve cover gasket is essential for preserving the proper functioning of the engine and protecting it from potential damage due to oil leakage.