What does filter housing O-ring mean in practice?
The flexible ring seals the connection between the filter bowl and the head by controlled compression in a clean groove.
When does it matter?
Grease will not repair a cut, flattened or stretched O-ring, and poor cross-section may prevent proper sealing.
Which solutions are related to it?
The seal is cleaned, inspected and lightly lubricated with a water-compatible agent; replaces the damaged one with exactly the right size.