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Sticky Diesel

Sticky Diesel
Pump Siezed from Sticky Diesel

“Sticky Diesel” - not a very scientific name but one that is becoming more common with increasing incidents of the sticky brown deposits clogging filters and literally jamming fuel pumps and injectors.

It is incredibly difficult to wash off your hands and more often than not is associated with the diesel smelling of a solvent like turpentine.

Sticky Diesel in Filter
Sticky Diesel in Filter mesh

So what going on??


It’s not an easy one and various theories abound but with the kind help of our corporate additive suppliers and their laboratories, we tested samples using Fourier Transform Infrared Spectroscopy (FTIR Spectra).

This showed clear evidence of a common Hydrogen Sulfide (H2S) scavenger MEA-Triazine. 

See following from a page in the report where the FTIR highlighted a 96% match of MEA-Triazine in a Marine 16 sample sent to us from a customer. The sample smelled of solvent.

H2S Hydrogen Sulfide Scavenger MEA-Triazine

This video is the sample from the lab. The customer had drained it out of the bottom of his Diesel Dipper, the MEA-Triazine is clearly visible and heavier than the diesel with an sg of 1.15.


Some background:

Modern crude contains a lot more sulphur than in the 1990’s and we now demand almost zero sulphur content in finished product. At the same time a modern refinery now extracts 50% more finished product than in the 90’s.

To achieve this, the crude is highly refined. It goes through many more process than a few decades ago to give us the Ultra Low Sulphur Diesel (ULSD) we have now.

We have a presentation here:

This ULSD is highly unstable, degrades rapidly and leaves deposits in the form of gumming and lacquering.

Sometimes, however, this ULSD finished product coming out of the refinery can be off specification and still contaminated with Hydrogen Sulfide. In order to ensure it meets specification an H2S scavenger additive is used, commonly, MEA-Triazine. This can, sometimes, carry over into the finished product, your diesel. That on it's own though is not too big a problem.

But that's only half the story...

.....Now, to make a bad situation worse, along comes the renewable fuels directive and the addition of a minimum % of Fatty Acid Methyl Ester (FAME), that’s the bio content in modern diesel.

Which incidentally comes from chopping down rain forests! I struggle to see how that’s environmentally friendly, but that another story!

But how is this translating into Sticky Diesel?

Working with the laboratories we now strongly suspect this MEA-Triazine is reacting with elements in the diesel.

We have found previously sterol glucosides (SG) from FAME and Sodium Soaps (Carboxylates) from reaction with the FAME can present as "hairy caterpillars" see following photo... Most often worse in diesel with a high water content (saturated diesel), the water acting as a catalyst.

The Sodium Soaps are formed in a reaction of the FAME with elemental metals found at the interface between the water and the diesel.

Bio diesel FAME in Fuel Filter
Sterol Glucosides and Sodium Soaps from FAME

We believe the MEA-Triazine is reacting with both these elements. It doesn't take much imagination to recognise how these "hairy Caterpillars" can become a sticky brown residue like toffee. AKA "Sticky Diesel".

So how can you protect yourself?

Our mantra here at Marine 16 is you must remove the water from your fuel tank, it is responsible for 85% of fuel problems. Our Diesel Fuel Complete (DFC) includes a demulsifier, specifically to help drop the water out of the fuel.

Be wary of fuel additives that are specifically designed to absorb water into the body of the fuel, whereas this was fine up to the late 1990’s it is probably the worst thing you can do in modern diesel. 

The fuel is already absorbing water from the atmosphere due to the hygroscopic FAME, absorbing more water off the bottom only makes the water saturation worse.

Additionally, to absorb the water, these additives can use alcohol or a derivative, Glycol etc. The alcohol can, in time, break down and oxidise leading to brown deposits on the bottom of the tank. This has been attributed to the Sticky Diesel problem but we cannot confirm that although we are testing.

....... Fit a Diesel Dipper to remove water and any contaminants as they are formed. Working whilst you are underway and the bottom of the tank is sloshing about it will clean everything off the bottom of the tank, even that behind the baffles and before it gets bad enough to be sucked into the fuel supply to the engine.

The customer who sent us the sample was very happy with his Diesel Dipper purchase as it removed the MEA-Triazine BEFORE it became a problem.

....and if you still need convincing why you need to get the water out, see this.....This is what happens inside your tank when you hit the breakwater, only you never see it.

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