What’s blocking your fuel filters?.

The diesel problems last year were well documented with social media posts clearly showing the frustration as operators needed to carry spare fuel filters in the cab ready to change when the machines stopped in the middle of a field!

What’s blocking your fuel filters?.


The diesel problems last year were well documented with social media posts clearly showing the frustration as operators needed to carry spare fuel filters in the cab ready to change when the machines stopped in the middle of a field!

The problem hasn’t gone away and is crystal clear, you should not have to change your fuel filter in the middle of a field but the filter plugging (blocking) was not the traditional black slimy sludge (diesel Bug) or hard shiny deposits (Asphaltenes). This is relatively new, resembling a soft white or brownish deposit that was coating the fuel filters

As members of the NAAC we heard first hand the frustration. We were hearing the same issues in marine and with inadequate explanation we set our stall out to find out exactly what this new contaminant was and if there was something we could do about it.

As market leaders in marine for fuel additives I lent on the excellent relationship we have had over the years with our corporate additive suppliers who made available their fuel laboratory testing facilities in Ellesmere port, indeed they were interested in a solution as much as us, this was all new stuff to everyone.

With the help from John Deere and the NFU we received samples of fuel and filters from farmers and contractors which resembled those we had received from a number of UK wide stockists in marine.

We sent the samples to the labs and following extensive tests which included Electron microscopic Xray, Infra Red Spectroscopy and Pyrolysis, I don’t know what they are either?? They identified the main cause which turns out to be Carboxylate Acid, or what the Victorians called…. Soap. But why and how?

Modern Diesel now has a bio content to meet the renewable fuels directive, this “Bio” is called FAME or Fatty Acid Methyl Ester and this is the root cause of the problem. Probably no great surprise to anyone, but it is not the FAME per se that is the problem, it is the quality, age and source of the FAME that is important, so just reducing FAME content is diesel is not going to solve the problem as was proposed in Scotland.

FAME is made from plant oil, typically Rape seed, Sunflower, Palm etc. It is made to a standard and tested at manufacture where it receives a “certificate of analysis”.

Antioxidants are added at manufacture in an attempt to slow the oxidation and degradation although plants have a high Vitamin E which is a natural antioxidant so do not require much, if any. However, FAME is also made from old cooking oil, Chip shop used oil etc. This of course has little antioxidant and needs a much greater dose of additive for it to meet specification. In reality though the bare minimum is added, it is after all a cost.

Once awarded a certificate it can be shipped to blend plants to be mixed with Diesel to create the modern fuel we use. However, that journey can take a number of months and like plants it starts oxidising, imagine a banana in a bowl, it’s the same thing. Depending on the transit time, what the blend plant receives can be very different to what was shipped, it should be tested at delivery not source but that’s another story.


This oxidative degradation cannot be stopped and one of the reasons why all the oil majors are unanimous instating diesel should not be stored longer than 6 months. Totally impractical of course because you can never empty a tank before topping it up so the problem must be mitigated.


So here is the issue, once this degrading FAME is in the diesel, and your fuel tank, the degradation continues at pace and begins to react with the Sodium and potassium metals etc in the diesel and forms acids. This is a form of carboxylate acid or soap which sinks to the bottom. This will happen quicker in the interface between the diesel and the water beneath it.

So what can be done about it?

Most importantly, my mantra as always, remove the water!. If you have a drain cock on the tank, use it, regularly, preferably weekly. The FAME content is highly hygroscopic and is literally sucking the moisture out of the air. A desiccant breather will help dry the air as the tank breathes.

If you don’t have a drain? Use a pipe and syphon it out or if you don’t want a mouth full of diesel get a Diesel Dipper which will do it for you. Additionally use a fuel additive with a high level of antioxidant such as Agri 16 Enhancer.

Last year, following the results from the lab, we improved our additives to include a strong antioxidant. Agri 16 Enhancer has a detergent, lubricant and antioxidant and will dose 4000 litres of diesel. These are the only additives you need for modern day diesel.

However bare in mind the degradation process can only be slowed, it cannot be reversed so don’t buy large volumes of diesel, buy what you need when you need it.


Peter Weide was a Chief Engineer at sea, Ship repair yard Director and latterly head of UK sales for Wärtsilä engine manufacturer. He is a co Director of Marine 16 and AGRI 16. Also the inventor of the Patented Diesel Dipper. He is always happy to answer queries and give advice.

sales@agri16.uk   www.agri16.uk


Back to ArticlesGet in TouchHome

About Agri 16

Agri16 products were developed exclusively for Agricultural Vehicles.  We make it easy for you to maintain your kit, inside and out.

Widely respected for our fuel treatments, we can eradicate diesel bug, remove harmful injector deposits and maintain the fuel system.  

Copyright Agri 16 - Design & Build AllAbout Sites