1. Turn off the fuel petcock (if fitted) to prevent fuel from draining or siphoning out of the tank,
2. Unscrew the T-handle on top of the filter and remove the cap.
3. After removing the top cover and T-handle, lift out the old filter element and place it into a plastic zippered bag for proper disposal. 
4. Remove and dispose of the rubber O-ring from the base of the threads on the T-handle.
5. Drop the new filter into the housing, and fill with fresh clean fuel.
6. Smear some clean fuel onto the surfaces of the new gasket and O-rings before carefully reseating them into their respective grooves.
7. Replace the cap, making sure the filter housing is correctly seated in the groove. 

1. The role of the oil-water separator removes the moisture in the diesel to reduce the failure of the fuel injector and prolong the service life of the engine. The principle is mainly based on the density difference between water and fuel, using the principle of gravity sedimentation to remove impurities and water separator, there are diffusion cones, filters and other separation elements inside. The oil-water separator also has other functions, such as pre-heating the fuel to prevent waxing, filtering impurities, etc.;
2. The automobile oil-water separator is an instrument that separates oil and moisture. In terms of mechanism, it is mainly divided into oil dewatering separator and water deoiling separator; in terms of usage, it is mainly divided into industrial grade oil-water separator, commercial oil-water separator and household oil-water separator;
3. In terms of separation principle, there are membrane filtration oil-water separators, oil-water separators using lipophilic materials, non-powered oil-water separators with different specific gravities, and demulsification oil-water separators with pharmacological effects.