Diesel filtration misinformation

Diesel filtration misinformation


It has become obvious through our searches for improved products and services that there is much misinformation being spread about diesel filtration.  What worse is, it’s coming from places and people who really should know better.  

Proper filtration of diesel fuel is the key to long service live of diesel injectors and pumps,  any business telling you that extra filtration and water separators are needed are in fact correct and by fitting these products to your vehicle you are doing the right thing.

The problems start when businesses recommend or sell you the wrong product through their own lack of knowledge on how filters work and how filters are rated.  I have found many businesses claiming that all common rail diesel engines use 2micron filters, or that a filters traps %100 of particles larger than its micron rating.  I’ve even found claims like “all late model diesel engine use 2micron filters”.

Unfortunately this sort of misinformation leads to people wasting money on products that either do nothing at all to improve the filtration in their fuel systems or only part of what is claimed.

Firstly we need to address how filters are rated. 
A micron rating without an efficiency is meaningless information and tells you nothing.  To put it another way, straining your diesel through and old pair of your underwear, some 2micron particles will be filtered out.  But you are not going to call your old undies a 2 micron filter and trust your engine to them, are you?.
You will find efficiency ratings expressed as either a % or a Beta ratio. A beta ratio of B100 is the same as saying %99 efficient.  A %99 efficiency (B100) means 99 out of 100 particles at the rated micron size will be trapped by the filter. (or 1 in every 100 will get through)
You may find some filters where multiple efficiencies are listed, Eg: %50@2 micron – %75@12 micron and %99@25 Micron.
Filters are tested using laboratory clean fuel and test dust that is of known size and amount. The fuel and test dust is pasted through the filter and the dust that passes through the filter is measured and counted and the efficiency of the filter is determined. 
By know you should be seeing that there will always be some dust/debris particles that will pass through the filters fitted to your vehicle.   

 beta ratio

Going back the statement made by some ‘diesel specialist workshops’ that “all modern diesel engines use 2 micron filters”.   They have not quantified their statement with an efficiency. Their statement is meaningless and only serves to sell their product.  

It is far more correct to say that all modern diesel engine SHOULD be using 2 micron filters with a Beta ratio of 100.  The problem is vehicle manufacturers don’t make the information about their filters available to us in the first place.  The proof that the factory filters and service intervals are substandard is in the number and types of injector failures the industry is seeing.   These failures can only be caused by dust damaging the valving in the diesel injectors.



The next problem we have is the rate of fuel flow through the filter will change the efficiency of the filter.  The greater the rate of flow through a given size filter, the lower the efficiency is going to be.
A filter that is suitable for a Hilux is not going to be suitable for a V8 diesel Land Cruiser. Although there are plenty of businesses willing to sell the same small filter kits as suitable for all diesel vehicles.

So far we have established that we can’t quantify the manufacturers’ filters without paying for costly Lab testing, but we can say they are substandard due the number and type of injector failures we are seeing. 
Micron rating without an efficiency are meaningless.
The size of the filter is very important and must be suitable for the flow rate of the fuel system.

So how does this all work in the real world as we driving our cars?  What happened when we fit say a 30micron %99 efficient filter before our original filter. 
The ‘pre’ filter will trap %99 of particles at or above its rating, as the particles get smaller, more and more of the particles will pass through the pre filter. It is then up to the original filter to finish the job.  If %90 of the 2-3-4-5micron particles passed through the pre filter and we the give the original filter a theoretical efficiency of %65@3 microns %31 of the original 3 micron particle load will be passing through and on to your injection pump and injectors.      The truth is some filters will not even be as efficient as %65.  

We also need to remember that laboratory testing also shows us that filter efficiency in an operating fuel system is not fixed and no filter will always work at its rated efficiency.  Efficiency will fluctuate constantly and will improve with dust loading of the filter, this will also be accompanied by increased restriction to flow.


This leaves up with some questions, What do we do? What do we spend our money on?  What if we’ve been sold the wrong thing?

I can answer these questions.  Firstly don’t spend your money with any business who simply has filter kits for sale, or who makes filter rating claims without an efficiency.
Buy from a business that takes the time to learn about the products they sell and who can demonstrate an understanding of the operation of the filters and fuel systems.

You should buy a product with micron/efficiency rating that will provide you with a reasonable amount of extra filtration.  This means 10-15 micronB100 pre filters or 2-3 micron B100 final filters.
These filters need to be of adequate size to slow the fuel flow down in the filter and to have a reasonable life.      

If you have been sold a 30micron pre filter, chances are we can supply you with replacement filter of the correct size and micron rating.