What you need to know about Clean Diesel ISO standards

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We get a lot of questions about ISO standards – and some of the most common questions are about clean diesel, or ISO 4406.

The standard 4406 basically calls for a quantifiable measurement of particulate contamination to achieve maximization of equipment performance and minimize repair and replacement issues and expenses.

But, there’s a lot more that goes into filtering, conditioning, and monitoring clean diesel. Let’s walk through it.



Coalescing deals with removing water and particles from the fuel. The main reason pumps and injectors fail? Water. And keeping the water out can be a challenge. That’s because there are many areas where water can be introduced. To prevent the water from creating damage, it’s important to recognize the signs.

Signs like erratic idling, or if the engine cuts out for a moment. Those are good indicators you may have a problem.

What you can do: try the Parker DI Series coalescer and DSO Series separator; they work with each other to separate and remove water from the fuel. These products meet the ISO 4406 standard and can clean up to 5,000 gallons per minute. 



When particulates get into your diesel, it can increase engine wear. That results in extensive downtime for repairs and maintenance – and is often the culprit of early parts failures.

The newer the fuel system, the more quickly particles can do their damage. Hard particulates in the fuel system can create difficulty when trying to start the engine, performance issues, and even complete engine failure.

While getting clean fuel isn’t too difficult, keeping it clean can be a challenge.

What you can do: try the Parker DFO Series filters. They’re a great product to use for particulate filtration, and can even lead to more efficient fuel consumption.



With this method, a chemical is added to the diesel that binds with water and particulates that can then be filtered out.

Even the most stringent diesel fuel providers cannot guarantee that water and abrasive particles will not make their way into your system at some point down the line. In fact, there are lots of ways your fuel can become contaminated, from the pipeline it traveled through to the tanks it was stored in. Even the engine the fuel is being used to power can be the culprit of contamination.

As your equipment creates mechanical friction, water particles are being created and carried through the system and into your fuel. If this has happened to you, you’re not alone. Carbon deposits are also a natural result of running your equipment and burning fuel. These deposits can also end up in your tank and start wreaking havoc.

What you can do: try the Aquacon AD Series from Parker. It’s a good example of a chemical binder on the market that works in conjunction with filters to make the cleaning process as effective as possible.


Don’t forget:

  • Clean diesel is easy to get, but hard to keep.
  • Contamination can occur at any time from the start of the supply chain to various points during consumption.
  • To keep your fuel clean and protect your engine, it’s important to take precautions and manage those precautions to ensure the productivity of your equipment.
  • Contaminated fuel can cause trauma to your engine and result in costly downtime and repairs. It can even shut you down completely.
  • By using a filtration system and changing it out every 20,000 to 40,000 miles, you will increase the life of your engine and reduce your maintenance downtime and improve the performance of your machine.

Have follow-up questions? Give our expert team a call; we’re here to help.