Donaldson P553004 (Volvo) With the interior tube required by Bosch for to compensate for pulsations
Mann W723 (equivalent for Volvo, but no center tube)
Toyofil diesel filter
Donaldson P557440
Donaldson P550385 looking from the clean end
Donaldson P550385 the dirt caught at the exit
Donaldson P550385 showing that it is about half dirty
Donaldson P550385 torn apart and stretched out to see the interior paper
A filter that says Nissan but is not.
The filter labeled as Nissan with rust inside
HP 619/1
A Donaldson Gasoline filter
A gasoline filter without a brand, all loose inside
Another rusty gasoline filter
Another gasoline filter
A collapsed original BMW filter
Cartridge from gasoline filter that came unglued from the housing
Gasoline filter that doesn't keep out much
Residuo dirt in bottom of diesel filter
Gel of bacteria in 4000 miles
Used fuel filters cut open
In order for the fuel injection system to have a long life without excessive soot or repairs, the fuel must be filtered to eliminate enything larger than 3 microns. Anything larger will either scratch or wear the internal parts or jam them.
Here we can see several technologies for filtering fuel, including features to compensate for pump vibrations and smooth out the flow of fuel to the engine.