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A modern diesel engine consumes only a small portion of the fuel it draws, the rest of the fuel circulates back to the tank.  Fuel water separator traps (as used by Water Watch) help in removing fuel contaminants by separating water and particles from the fuel in every cycle without any restriction to the flow of fuel through the system.  

  • A fuel-water separator has the ability to remove free, dispersed and emulsified water and particles with greater than 95% efficiency.

  • Research indicates that in high pressure fuel systems typical of common rail, mechanical filtration (filters) is extremely difficult, as not all dispersed and emulsified water can be captured by even the most advanced filters, which your factory fitted filter is.

  • Modern common rail systems are typically equipped with a "Water In Fuel" warning light to alert operators to the presence of free water, but those warning lights are not activated by untreated emulsified water (commonly found in motor vehicles).

  • Secondary filters will cause a restriction to fuel flow in Common Rail Diesel vehicles because the filter medium is a physical barrier designed to trap particles.

  • Placing a secondary filter on a vehicle is a duplication of the OEM filter already on the vehicle – which provides little protection against water damage. 

  • Original Equipment Manufacturer (OEM) vehicle fuel filter is a sedimentation and coalescent type, containing a water trap, which does not cope with providing water entrapment at the high flow rates experienced in a CRD system, eg. 60 Litres/Hr. for a typical 3 Litre engine. Damage debris is continually cycled around the system.

​Is there anything you can do to protect your diesel?

  • Yes - for WATER we recommend that you have a "Water Watch unit" fitted (its a water separator and detection system - not a filter - filters can only remove particles - Water Watch removes fluids and particles from fuel flow under pressure and at high temperatures) 

  • For PETROL CONTAMINATION, we recommend you install a "Diesel Key" - to ensure that you don't accidentally fill up with petrol or worse still, Ad-Blue.   No - you can't use a high flow filler with it, but that not advisable unless you're driving a large commercial vehicle (it can be removed on occasions where needed).

  • For DUST, you should extend your fuel tank breather to a place in your engine bay - especially if you are driving on dirt roads or exposed to fine dust particles.  


Water Watch with dirt caught in the bowl

Cooma Diesel Service Canberra
Cooma Diesel Service Canberra
Cooma Diesel Service Canberra

Contaminated fuel samples (left to right)

1 Rust, 2 Water, 3 Dispersed Water, 4 Dirt

Genuine factory fuel filters are technologically very advanced and fitted with a restriction alarm. 

Contaminated Diesel Fuel can not only destroy your Pump, Injectors, Common Rail, Fuel Tank and fuel lines.........
but also your engine.

At Cooma Diesel we see many cases of fuel contamination every week.  As Australian Choice Magazine reported in February 2017 "more than 673 contaminated fuel claims were made to insurance companies last year"

That's just the tip of the iceberg - many people don't have insurance cover. 

What causes diesel fuel contamination issues:-

  • Water in diesel is probably the number one issue

  • Accidentally putting petrol or Ad-Blue into a diesel vehicle 

  • Dust drawn into the fuel tank via the tank breather


What happens - water in your diesel causes all metal components to rust - very quickly (almost instantaneously due to the heat of the fuel) and this is then pushed at high pressure through all the components of your fuel system causing wear and damage.  Dust results in the same abrasive wear to components while petrol and Ad-Blue strip all the lubrication from components causing catastrophic damage.

How do I know if I have contaminated fuel in my vehicle?

  • Engine running rough, lacking power or performance

  • Harder to start or won't start at all

  • Engine, restriction or fault light illuminated

Do not continue to drive your vehicle -

the further you drive, the more expensive the repair bill will become.

Secondary filters are at best duplicating your Original Factory Filter, but they add a huge amount of restriction to the flow of your fuel through the system which can cause damage as well as impacting on the performance of your diesel.


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