Describe difference between mechanical seal and oil seal – Whether it is a mechanical seal or oil seal, it prevents the fluid seeping the liquid to other parts of the machine, or it keeps the rotating parts lubricated.

ERIKS type GV (type C according to DIN) is equivalent to type M, but is a heavy-duty version with a double metal casing. This can be a useful solution with larger diameters in more demanding applications. There is also a version of this type with a dust lip; the GVST (type CS according to DIN).
Type B Oil seals
THE 6 GUIDELINES ARE:
One common reason leaking occurs in engines is that debris is caught in the fork seal, holding it open and allowing oil to sneak by. So, how do you fix this? This is where the little circular devices come in—oil seals.

(JIS* SUS304)

If this is not possible, you may be able to fit the lower retaining bolt into the upper mounting support, to hold the engine level. Or the gearbox may have to be jacked up and supported.
The allowable total eccentricity is the maximum total eccentricity at which the sealing edge can accommodate shaft rotation and retain adequate sealing performance. The oil seal's allowable total eccentricity is affected by the design of the oil seal, the accuracy of the shaft, and the operating conditions.