The Purpose of an anti drain back valve.

The Filter Guys

What is the Purpose of an anti drain back valve?

Modern engines are engineered to an extremely delicate manufacture and need to avoid any kind of wear and tear caused by starting and operating them. Oil is essential to lubricate moving parts to avoid wear particles being created which can cause problems and is also necessary to carry such particles back to the sump or to the oil filter.

Many modern oil filter canisters have inbuilt anti drain back valves which serve two important functions. The first is: if the canister is mounted side-on or at a slight angle. It helps avoid any air that may be in the system getting trapped in filters mounted in such a way. By not allowing the oil to drain back to the sump air cannot be drawn into the system. Trapped air can cause an ‘air lock’ effecting the filters operation. Also any trapped air can also be pushed through the system causing moments of ‘dry wear.’ Dry wear is when moving parts rub against each other without oil present, this is how particles can be introduced into the system and damage can be caused such as seizing.

The second function is simply to stop the oil from completely draining from the engine when it’s not running. This means that from the moment that you start your engine it is lubricated which helps prevent a cold start causing dry wear and tear as previously mentioned.

It is important that if the OEM filters do contain an anti drain back valve that you use the correct aftermarket product. At Sterling Filtration we have an extensive cross referencing service to make sure that you get a specification-correct alternative rather than simply a will fit option.