The New Diesel Fuel & Inland Boaters.


As from January 1st 2011 the EU has decreed that fuel for all "off road" equipment shall be low sulphur and this includes the fuel used by leisure boaters in the UK. The UK fuel suppliers have said they will meet this obligation but supplying dyed EN590 DERV – that means we will be buying the same fuel as we use in diesel vehicles but with a red dye in it. This means we will also being supplied with fuel that at the moment contains up to 7% bio-fuel (B7) and the EU have plans to gradually increase this proportion over the coming years.

This raises a number of issues for boaters, especially boaters who have been a bit slack on their fuel system maintenance. We will look at these issues one by one and suggest solutions.

The good news

In general terms EN590 DERV is a more satisfactory product for diesel engines and some may notice the engine produces slightly more power or a slightly lower fuel consumption whilst the engine may be slightly quieter. This is related to the typically slightly higher calorific value and cetane rating. I doubt many boaters will notice the difference though.

The problems

Low Sulphur

Concerns have been raised over the lower sulphur content of EN590 DERV delivering less lubrication to the injection equipment than the old high sulphur fuel. However the EN590 standard includes a lubricity standard so this concern is probably unfounded.

The Bio Content

This is where my (and many others’) main concerns are focused.

First of all speakers form the fuel industry at a fuels conference I attended earlier this month were very clear that the EN14214 for bio-diesel is deficient, especially in respect of enforcing compliance with the standard and that much of the bio-diesel available for blending with petro-diesel is substandard. Often the bio-diesel contain far too much water and this has caused the Germans and at least one fuel company to introduce their own standards allowing a far lower water content than EN14214. Unfortunately as end users boaters have no control over what they are being sold.

A selection of yeasts moulds and microbes, collectively known as diesel bug, breed at the interface between fuel and water. Whilst the petro-diesel content will normally sit above the water the bio content will absorb water. This increases the surface area of the interface giving the bug a greater opportunity to breed. Of particular concern to me was a statement and pictures provided by one of the suppliers to supermarket forecourts. They showed that despite the high turnover of fuel the bulk tanks are suffering for the growth of bug that has got as far as blocking the filters on the pumps. This is with EN590 B7 fuel. Supermarkets and large transport companies with their own bulk tanks can afford to employ fuel polishing companies to filter the bug from their bulk tanks. I wonder about waterside outlets.

Bio-diesel will cause some types of "rubber" seals and pipes to degrade over time but of a greater concern at the moment is that seals tended to swell using the old diesel but now the low sulphur content will tend to allow them to shrink back to their original size over time. (from an ex-CAV test engineer). If any fuel system parts are more than about 8 to 10 years old they may suffer in this way.

The bio content is also a far better solvent than ordinary diesel so it is to be expected that more dirt and glazes from the fuel tank and pipes will be passed to the engine in the fuel until it has all been removed.

Bio-diesel tends to break down over time so there are questions about how long it is wise to store it. The ex-CAV engineer also said that copper accelerates this breakdown so there may be questions over the use of copper fuel pipes.

Bio also evaporates at a much higher temperature than ordinary diesel so any that finds its way past the piston into the engine oil is likely to stay there diluting the oil. The commercial vehicle manufacturers demand a shorter oil change interval if high percentages of bio-diesel are used.

Solving the problems

Luckily our fuels will be a blend with, at present, a small bio content. It will also comply with the same standard as road fuel so there is more incentive for the supplier not to supply poor fuel.

I will look at each problem in order of ease of solving.

Oil Dilution from Piston Blow By

Most marine engines operate on a very short oil change interval when compared with road vehicles and this may well be due to inland engines never getting the oil hot enough to evaporate ordinary diesel from the sump so I do not expect any problems from dilution cause by blow by.

Copper pipes

My advice is to keep a watching brief on this one and take no action until a problem actually occurs. In any case many boats use steel pipes.

The Solvent Effect

With only a 7% bio content this effect will be considerably reduced so as long as you are sticking to your manufacturer’s filter change intervals I do not expect a major problem. I would not let my filters stay in place for more than two years if I did not reach the manufacturer’s change period. It might be a good idea to carry spare filters and know how to change them and bleed the system, but this is only precautionary.


The rubber seals

The main problem will probably show on engines where the seals have worn but leaks have been prevented by the swelling. I think these will leak long before any problems caused by the bio-fuel show themselves.

There are no seals inside the majority of injectors so we are only concerned about the fuel lift and injector pumps so boaters would be well advised to inspect their engines to see if they have a lift pump driven by the engine (a lot of modern ones are electric) and if the injector pump is bolted into or on the engine in such a way that if the shaft leaked fuel would find its way inside the engine. In reality it is only likely to be some of the vintage engines using a gravity feed from a day tank that will not have to worry.

Most boaters will need to take precautions. These really centre on ensuring the engine oil level is NOT rising and feeling and smelling the oil every time you dip the sump to ensure the oil is not diluting. External fuel leaks are unlikely to be massive in the first instance so regular inspections for leaks will indicate when the equipment needs sending away for overhaul and the seals changing.

Breakdown over Time

Beta stored some 100% bio-diesel for over six months with no signs of deterioration, but this was without any water in the container. The fuel companies say you should turn the fuel over within two to six month (depending upon who is talking to you). Once again the low percentage of bio will help us, but it would be a good idea to try to run the tank very low before refilling during the summer. This should minimise the time you keep the fuel in store. The problems related to water means that it would not be a good idea to keep the tank partially empty during the winter.


I am convinced that this is the main area where problem will occur, especially on narrowboats that in general are NOT fitted with adequate fuel tank drain taps.

Boaters should strive to remove the water from the bottom of the tank. In most narrowboats the only practical way is to use a pump and length of pipe through the fuel filler. Causing the boat to list towards filler will help to concentrate the water in an area you can get at.

Do not just pump out water, also pump out and dispose of any fuel that appears cloudy. This is likely to be bug before it develops into filter blocking jelly. This should be an annual job.

At the very least use a fuel additive that removes water from the fuel and on older boats with fuel tanks in an unknown condition it might be a good idea to use one that contains a biocide as well like Marine 16.

The problems with EN590 B7 on forecourts indicates that many marinas will not be able to look after their fuel well enough and will not have a fast enough turn over. It would be a very good idea to only buy fuel from suppliers who:-

Have the highest turnover you can find.

Would find it very expensive to supply contaminated fuel.

This probably means hire fleets.

Try to be present when your fuel filters are changed so you can inspect the fuel that remains in them and their parts for signs of cloudy fuel or jelly like substances. If you find any immediately use a high dose of biocide additive.


All of this sounds alarming but I do not anticipate any major problems for well-maintained boats where the fuel tanks are kept as water free as possible. I do expect problems with old boats that have not been well maintained – especially in respect of fuel bug.


Please note that I have just had a communication from Marine 16 that I have not had time to study. This suggests they will be marketing an A & B type biocide additive for use alternately. This should go some way to allaying fears about the bugs building up resistance to biocide.

Marine 16 also market a bio-test kit so retailers and end users can monitor the level of bug in their fuel. I think retailers should start monitoring at least twice a year and boaters may want to try it once a year as well.

Please further note that I have no commercial connection with Marine 16 and have been critical of their products in the pass. They are, however, the only additive company who keeps me informed of development.

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