This week our wonderful blogger Jonty Pearce is contemplating fuel options


As a Brummie, I feel qualified to reproduce a shortened version of this very bad Black Country joke as an opener to this whimsy. Having been made redundant, Enoch and Eli approach the employment exchange where the clerk asked Enoch his occupation. ‘Panty Stitcher’ replied Enoch. ‘I sew da elastic onto ladies’ panties and tongs’. Looking up the said job, the clerk awarded him £80 weekly. When Eli was asked his occupation he replied ‘Diesel Fitter’ whereupon he was awarded £160 a week. When Enoch heard this he went back to find out why he was paid less. The clerk replied that a Panty Stitcher is listed as an unskilled job while a Diesel Fitter is a skilled job. ‘What skill?’ yelled Enoch. ‘I sew da elastic on da panties and tongs and Eli dust puts dem over his head and says ‘Yep – diesel fitter.’

Well, I suspect that I might have to take up the role of a diesel fitter, but specialising in fuel redirection rather than panty fitting. And the problem facing me? A 260 litre fuel tank whose capacity lasts me at least a season full of potentially mouldy red diesel. Good old-fashioned sulphur-laden diesel was far less hygroscopic than the modern FAME (Fatty Acid Methyl Ester) containing biodiesel now on offer at the majority of marine diesel pumps. While fuel producers have taken steps to ensure that the diesel should be in good condition when put in the supplier’s tanks, the problems actually start once the fuel is dispensed into our own tanks. Especially when it might sit there for a season or more during which the FAME attracts moisture which allows organisms – diesel bug – to grow. Add the problem of condensation, and water collects in the bottom of the tank providing the fuel bugs with all they need for proliferation.

The responsibility for the fuel in our tanks lies on our shoulders. There are precautions we can take to prevent the occurrence of these problems – principally by keeping the tank full to eliminate condensation and by keeping diesel usage high. Be careful of what fuel you buy; ask the supplier for details, and use a source that is regularly refreshed. But by keeping a large tank full all the time we are perpetuating the problem of our low fuel usage and resultant stale diesel. Additives and biocides can be used to break down the organisms so that they pass through filters and remove the water that is required for organisms to grow. However, FAME is a good solvent that can break up the sludge found in the bottom of most fuel tanks which, if stirred up, blocks our filters. It is therefore a good idea to keep your tank clean as well as use your boat regularly. Just as the icing on the cake, be aware that while newer diesel engines are FAME resistant, the seals and hoses in older engines might be damaged by the new fuel formulation.

So, while better for the environment, biodiesel presents sailors with problems. I was careful to cut an access hatch in my fuel tank when I bought Aurial – gladly there was only a little dirt and I have been careful to keep the tank full(ish) and to use additives. However, I am in no doubt that I am not using diesel fast enough to keep it fresh, and suspect that the problem will only get worse. Apart from using Aurial more, I could remove the perfectly good, and relatively new, large stainless steel fuel tank and replace it with a smaller version backed up by 20 litre containers for long trips. Alternatively, I could fit a ‘superfilter’ or install a diesel polishing system that would intermittently cycle the diesel through a filtration system. I do not include the use of white diesel here as an option – it suffers the same problems.

When discussing it with The Boss, her first instinct was ‘don’t reduce the size of the tank – we’ll need it when we retire and sail round Britain’. A fair comment, especially as removal of our tank would be a destructive process either to the tank itself or the side of the cockpit. I suspect that a diesel decontamination ‘superfilter’ will soon be on our shopping list – I have seen a version that efficiently separates water as well as filtering the fuel through a 30 micron stainless washable filter.

I am, however, investigating whether this is really adequate. While it will cleanse the diesel coming from the tank on its way to the engine, it will not be enough keep the fuel in the tank itself in good condition – for that I am relying on additives. I suspect that a polishing system running either on a timer (if on shore power) or permanently when the engine is in use would keep the diesel in better condition. I am aware that a fair proportion of fuel ends up back in the tank via the fuel return pipe – but is that enough to keep the diesel fresh? I took advice from Ian Curry from Fuel-Guard, manufacturers of the FDG100 fuel filter that tops my wish list. He suggested installing one of these washable filter units plumbed in not only as a normal filter, but also with a T-junction after the FDG100 to divert the fuel line via a timed fuel pump back to the tank, using the existing fuel return line. This should operate as a cost efficient fuel polishing unit that will keep my cleansed diesel happy. I hope to report back when I have more answers, but would welcome any other ideas. Yachting Monthly will pass emails on to me via

On Fuel-Guard’s website Ian Curry stars in a video which finishes with him quaffing back water that the FDG100 has separated from the fuel. I have no plans to emulate him – I’ll stick with a pint of good old pale ale.

– Jonty Pearce