Table 3: Requirements
Seals perform best when they are lubricated, however, some machines quickly go on dry spells. So, in cases like this, choosing a leather or PTFE seal is the right decision to make as both of them can function with less lubrication than other types of seals.
With minor lip type Used for applications where there are contaminants, such as dust and foreign matter, on the air side face of the oil seal.

: prevents particles from reaching the sealing lip.