The purpose of the oil seals is

ERIKS type M (type B according to the DIN standard) has a single metal casing and rubber sealing lip. Since the casing is made of metal, it must be fitted in a well-finished, undamaged groove. Large volumes of oil seals with metal casings are often cheaper, which is why they are often used as original equipment in machines. However, if an oil seal has to be replaced, types with a rubber exterior (type R or RST) are easier to fit. Type MST is similar to M and commonly used. The difference is the dust lip in the MST oil seal that prevents dust and dirt reaching the sealing lip, and extends its service life in dusty environments.

Silicone Oil Seals - Designed to absorb lubricants in order to lessen wear and friction, silicone rotary shafts also offer high thermal resistance and a large temperature range. But, they do not handle abrasions well or interact with oxidized oils.

On most cars you need to remove several parts to get at the seal.

Bauerle and Bruhnke⁷ found that aeration reduces the effect of oil additives on fluoroelastomer properties. Some of their data is reproduced in Fig. 14.4,⁵ showing the effect of aeration of an SF-grade 5W30 oil on the retention of elongation of a VDF/HFP copolymer (FKM-E430), a VDF/HFP/TFE terpolymer (FKM-B600), and a VDF/PMVE/TFE fluoroelastomer (FKM-GFLT). The HFP-containing polymers show much better retention of properties with aeration.

These new oil seals can also be equipped with a shaft rotation sensor.