Comparing Fuel Filters & Micron Ratings


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The technologies being used in fuel systems on vehicles are advancing at an unprecedented rate with modern sytems providing new levels of operational efficiency and reliability. The higher pressures used, with reduced tolerances, require exceptionally clean fuel.

We are frequently asked by customers concerned about their fuel cleanliness "what micron rating is my current filter" and "do you have a finer micron filter I can use"?

The published micron rating, (or particle size that a filter captures), does not provide an understanding of the performance of the filter unless you also know the efficiency at which it is measured. The efficiency of a liquid filter on a given particle size is frequently described as either a Beta ratio (ß), or as a percentage (%).

Two filters that both claim to capture the same size particles or have the same micron rating may provide vastly different performance results.

For example, when comparing two filters that are both rated at 5 micron, if filter A has an efficiency of 99% it will remove 99% of contaminant 5 micron and larger from the fluid. If filter B has an efficiency of 50% it will only remove 50%, or half, of the same contaminant from your fuel. Filter B may allow up to 50 times more contamination to pass than filter A, a very different level of performance!

The higher levels of contamination in your fluid may result in accelerated wear, and ultimately, the premature failures of components.

Commonly used fuel filters may have multiple efficiency ratings describing their performance.

For example, a filter may be described as being 50% efficient on 2 micron particles, 75% efficient on 12 micron particles and 98% on 23 micron particles.

Micron_Rating_-_99_at_5_micron.png  Micron_Rating_-_50_at_5_micron.png

You cannot guess the efficiency of a liquid filter.

Particle or micron sizing means little without a measure of effiency. Efficiency does not describe a filter without a micron size.


Both the Beta ratio and percentages of efficiency compare the amount of contamination before and after the filter.

The table below provides the efficiency percentages of the commonly used Beta ratios.

Generally, efficiencies are not provided for micron ratings or partcile sizes smaller than 3 micron.

When looking at the different fuel filters, it is important to compare apples with apples when considering filtration performance.


Always consult your Donaldson representative for specalist advice.