[Kenth]

It´s an engine safety device.

[Sirrotica]

A correct Pontiac oil filter does not have a bypass valve incorporated into the oil filter. Many other brands do have a bypass incorporated into the filter, Pontiac however, does not.

Pontiac engineers choose to build the bypass into the oil filter adapter, rather than incorporate it into the oil filter itself. The purpose is to not allow the hydraulic pressure to damage the filter element by tearing it, or collapsing it in a situation of thick oil upon cold startup, or a nearly blocked filter element due to neglect.

The spring and the disc in the filter housing only reacts to pressure differential between the pressure of the pump side of the filter element and the downstream side, kind of an equalizing valve to operate when there is too much pressure differential. It's not meant to stand the entire pressure of the system, and is not engineered to do so.

It's a safety valve, as has been already stated so the filter element isn't collapsed due to hydraulic pressure differential between the opposite sides of the filter element. There are some people that block this valve in an effort to make 100% of the oil travel through the filter element. The risk is that the element will tear, dumping all the accumulated trash from one side of the element into the engine. Not something I would want to happen inside of one of my own engines, I've never blocked the bypass valve in any of my race, or street engines.

Unless someone dissected every one of their oil filters upon removal, you would never know the filter element had ruptured. If someone wants to have the oil filtered to a higher standard, a by pass oil filter can be used in addition to the standard issue factory element. It will keep the oil much cleaner than the 30-40 micron standard issue filter does as they efficiently filter to the 5 micron range. This adds to oil, as well as engine longevity.