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The Importance of Clean Fuel

Manufacturers of diesel engines are utilizing new technologies to meet the stringent requirement of tightening emissions regulations.

The High Pressure Common Rail (HPCR) Fuel Injection System has been broadly accepted by light and heavy diesel engine manufacturers as an integral part of meeting these new regulations. HPCR systems often operate at pressure between 27,000 and 45,000 psi.

Common rail fuel system components operate under these pressure ranges multiple times every minute and they simply do not have tolerance for dirty, wet or contaminated fuel! In fact, it is now being observed that particles in the size range of bacteria are creating wear, or erosion. Erosion has a detrimental effect on the injectors' ability to seal, and contamination is frequently linked to premature fuel pump failure.

In order to protect fuel systems, many diesel engine manufacturers now specify the required cleanliness level of supplied fuel. Tank contamination in excess of that specification may have warranty implications. On board filtration is designed relative to specified cleanliness levels.

Common Industry ISO Cleanliness Ratings

ISO 22/21/18 - Common cleanliness level of fluid
ISO 18/16/13 - Target rating for heavy gear/engine oils
ISO 16/14/11 - Target rating for hydraulic/transmission oils
ISO 14/13/11 - Target rating for diesel fuel

Fuels typically leave refineries clean, but contamination levels increase and occur throughout the shipment and distribution process. Most contaminants found in bulk fuel systems occur either as the result of poor handling practices and aged/inappropriate infrastructures.

Common contaminants include: rust, scale, airborne dust, various types of oxidation sludge, bacteria, water (from condensation, rain or wash water) and fuel additives which can turn insoluble after excessive storage periods.

Clean. Protect. Polish.

Donaldson not only provides on board filtration protection but also offers a complete range of user friendly bulk filtration systems utilizing industry leading technologies designed to protect your systems now and in the future.

  1. Clean before going into storage
  2. Protect fluids and it clean while in storage
  3. Polish it at the dispensing point


It’s not the filter's fault that blocking occurs. The filter is actually doing what it’s designed to do. Putting on a coarser filter than what is recommended will allow more contamination to pass.


The introduction of new fuels such as Ultra Low Sulfur Diesel and Biodiesel have introduced new corrosion and complex contamination problems; previously stable additives can now react to form gels and sludge.

A sudden increase in the filters blocking is a good indication that there is a chemical change in the fuel or oil. Generally bacteria or chemical changes in fuels or oils will block filters far more rapidly than any particulate contamination.

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