This seal is installed on the front of the crankshaft. It is recommended to change this seal out when you change the timing belt and water pump. This seal usually lasts around 150k miles before it starts to show signs of leaking. The timing belt and water pump should be changed at 100k mile intervals. The problem is that the front main oil seal can start to leak before the next timing belt change is due. Replace this seal when you do the timing belt and water pump for some peace of mind.
