Special exceptions still apply within the Volkswagen group. With PTFE oil seals, an aluminium or plastic housing is used in many different engine series. The Top Dead Centre (TDC) signal is no longer measured at the flywheel, but directly using a sensor on the rear crankshaft flange and integrated sensor in the oil seal. Special procedures and tools must be used for the disassembly and assembly of these parts.

1 .Material: There are 7 types of material used for oil seals, they are.

2. The most common types of oil seals are rubber-cased and metal-cased.
Oil seals come in various shapes to fit the machines and substances to be sealed.
Figure 2 shows the structure and the names of the various components of the most typical oil seal.
The functions of the various components are also indicated in Table 1.
Dynamic seals called bearing isolators are used to shield bearings from external impurities. They are revolving (rotor) and stationary (stator) elements. O-rings or strong seals are used in some bearing isolators, while they are constructed like labyrinths in others.