Nitrile is the most widely used rubber (elastomer) and it’s recommended as the best for almost all standard applications. This is solely due to the fact that nitrile has some intrinsic properties, such as low cost and compatibility with most environments. Some of the general applications of nitrile are non-latex gloves, automotive transmission belts, footwear, gaskets, synthetic leather, hoses, o-rings, and oil seals.

Rotary Wheel Of Auto Parts
Oil seal characteristics

A spring, the composition of which depends on the type
Rotary Wheel Of Auto Parts
Polyacrylate Oil Seals - Mostly selected for automotive and transmission uses, polyacrylate seals are able to withstand fuel, oil, ozone, sunlight and weather when used. With cars exposed to all these different fluids and elements, they are the perfect choice. However, they should not be used in low temperatures, as their flexibility weakens when cold.
What Benefits Do Oil Seals Provide?
Standard 3760/3761
VMQ (silicone)

oil valve cover gasket. It is important to ensure that the gasket is installed correctly and that the valve cover is tightened to the manufacturer's specifications to prevent leaks.
ERIKS

The black color of these spark plugs is a result of carbon buildup, which is a common issue that can occur over time due to normal engine wear and tear. This carbon buildup can negatively impact the performance of the spark plug, leading to misfires, rough idling, and poor fuel efficiency. It is important to regularly inspect and replace black spark plugs to ensure optimal engine performance.
If necessary, lever it gently with a broad screwdriver blade, but take care not to bend the flange or damage the head.