Nitrile rubber offers good durability for general use, while the flexibility of the spring behind the sealing lip keeps the oil seal firmly in place against the moving part.


The History and Applications of Oil Seals
No.
Because of the higher temperature resistance of FKM, this material is also chosen for applications where higher speeds play a role, which raise the temperature at the sealing lip considerably. Usually, using FKM will result in a longer life than using NBR. This compensates the higher price of FKM compared to NBR, as an FKM does not have to be replaced as frequently. The low temperature resistance of standard FKM is limited to -15 ˚C.
Environmental Considerations and Compliance
The most common oil seals are the ERIKS types R, RST, M and MST, which correspond respectively to types A, AS, B and BS according to DIN 3760/ISO 6194.
Installation
BS



Many oil seals are capable of resisting contact with grease, fuel, water, and other elements. Knowing what type of fluid the seal will interact with will help you choose the right oil seal that can withstand those types of fluids.
Metal case
Table 2 a): Common types of oil seals (with spring)