An overview of the different standard types of oil seals and their main characteristics is shown below.
First, an elastomer, most often nitrile, is vulcanised to a metal ring. This creates a stiffening effect that includes a specialised metal tension spring directly behind the sealing lip, keeping the oil seal firmly in place against the moving part.
Oil seals are always exposed to a lot of chemicals, both mild and harsh chemicals. The seals react by showing some signs like cracks, blisters, and discoloration especially when the chemical is harsh. This clearly shows that the chemical is not compatible with the seal, which goes as far as affecting its cross-link density (increase or decrease). When the cross-link density increases, the seal material becomes harder, but when it decreases, the seal material becomes softer.
Regular maintenance checks should include inspecting the condition of the valve cover gasket and bolts. Any sign of wear, such as rust or stripped threads, should prompt immediate replacement. When replacing the gasket, it's crucial to follow the manufacturer's guidelines for bolt torque and sequence to avoid potential problems.