Why Cheap Filters Can Damage Machines
Weak media, poor bypass valves and bad seals can turn a cheap element into a source of contamination.
Media migration
Poorly bonded media can shed fibres under high flow. The element then adds contamination to the system instead of removing it.
Bypass valves
Many elements include a bypass valve that opens when the element clogs, so the machine is not starved of oil. A poorly made valve can stick shut and starve the pump, or stick open and let oil pass unfiltered.
Seals and fit
An element that does not seal properly in its housing lets fluid flow around the media. It can look fine at every change while doing very little filtering.