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You mean I need to maintain this?

Fuel filter maintenance is more important today, than any time in the past given the common rail design and tight tolerances.


See below data from Cummins.

To meet today’s stringent emission regulations, fuel system injection pressures are extremely high (up to 37,000 PSI) to achieve better and cleaner combustion utilizing multiple injections resulting in optimal combustion and better fuel economy. As a consequence, clearances between the moving parts and the higher number of very small nozzle holes found in injectors all need improved protection from erosion. 50% of the worldwide diesel fuel supply does not meet OEM specifications for cleanliness; particles greater than 4 microns in size are known to cause wear to these sensitive systems. By way of calibration, human hair is typically 50 to 70 microns in diameter, a red blood cell is 8 microns and bacteria are typically 2 microns. The smallest particle which can be seen by the human eye without any magnification is 40 microns! To meet these demanding requirements, much finer filtration requires special media.


  • Dirt and sediment – will result in blockage of the filter and increased wear within the fuel system.

  • Water – is the greatest concern because it is the most common. It can be introduced into the fuel during the refueling process: through condensation inside the fuel storage tank, and or due to poor house-keeping practices. The effects of water in diesel fuel can be serious, causing injector tips to blow off, corrosion and reduced fuel lubricity, resulting in premature wear to pumps and injectors.

  • Organic contaminants – Asphaltines and paraffin wax, which are residual components from the refining process, will block screens, strainers, filters and even hoses.

Refer to the graphic for the specifications of a Davco 245, as an example. The Micron value is 8. Since the smallest particle to be seen by the human eye is 40, means you can’t tell when it’s time to change the filter by observation. The Restriction filter has to be used to determine when the filter requires changing. Some manufactures require changing every 25K miles. Notice the water removal difference in NEW vs END OF LIFE elements (same chart), which is another reason to change filters on a regular basis.


Given all this, it’s hugely important today that when a filter is changed, that the tech not fill the container with fuel from any external source since contamination could easily be introduced into the clean side of the filter causing the issues noted above. The proper way to change filters is to drain the fuel, replace the element, and use the manual or electric engine pump to pull fuel from the tank/s, ensuring that all the fuel is properly filtered.

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