The insides of a good oil filter

When you cut a good filter the pieces will pop apart from the pressure of a strong spring that will hold it against the retention valve and avoid draining back when the engine stops.

The relief valve pressure is designed for each application and must be made so it will not stick open or closed.

The base has to be strong, but flat to permit the functioning of the retention valve, and this valve has to remain soft and flexible at operating temperatures and engine oil chemistry for the entire period of the oil change.

The structure of the "paper" or filter media has to be deep enough and strong enough to not collapse, and should have ridges to avoid flexing and sticking.

The center tube has to resist presions and permit high flow, while staying smooth and having the holes sheltered from cutting the filter media while it vibrates.

All of the pieces after cutting

A good relief valve that won't get stuck

A solid base without barbs and a retention valve that won't harden

A good, sealed cartridge

A strong filter media to resist pressures and collapse

A center tube without sharp edges, but with enough holes for a good flow

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