2.2 Ecotec Anti drainback Valve For Oil Filter

[Spudislander]

The better conventional screw-on type oil filter has an anti-drainback valve to prevent oil from draining back out of the filter when the motor is stopped. However, this does not appear to be the case for the new 2.2 ecotec which has the top mounted filter element under a plastic cover. When changing the oil and filter on the new ecotec, I found that the oil drains internally from the filter because when I remove the cover it is already empty of oil.

Therefore, does anybody know what system compensates for the usual anti-drainback valve?

[Spudislander]

Further to my initial posting, I also contacted GM who provided the following response:

"The anti-drain back valve is used only on engines that require instant oil
on strartup and without the valve would knock due to a 'dry' engine. The Ecotec engines are able to supply oil throughout the engine very quickly due to an efficient design of oil paths and the pump itself resulting in not requiring the anti-drain back valve."