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Recently I have been asked by clients if they can safely use ordinary white road diesel in their boat. The complications regarding pricing of red diesel has tempted many boat owners to simply fill up cans of road diesel from garages as red and white diesel now cost roughly the same. That is if you do not count the 60/40 rule which only applies if you have an Ebespatcher heater or run your boats engine not underload just to charge your batteries or heat up a calorifer. (not as propulsion). Several clients have been concerned, as they have read in the press that white road diesel contains a percentage of bio-fuel, which they have heard does not store well and can dissolve fuel lines, filters and GRP tanks. I found this question interesting and decided to investigate by contacting Shell, Esso, engine makers such as Volvo and Yanmar plus suppliers of red diesel such as oil dealers, marinas and boatyards.

In theory road diesel should be better for your engine as it is a much more refined fuel and has a higher cetane level. Red diesel is more basic and has a high level of sulphur. The level of sulphur in red diesel is said to be between 500 and 1,000 parts per million (PPM) whilst road diesel is filtered to only 15ppm. Apparently sulphur is very bad for the enviroment.

The cetane level is a measure of how much heat the fuel will give off when burnt. The cetane level of red diesel is said to be around 42 but white diesel is supposed to be around 52. Therefore you would assume that a vessel run on white diesel would go faster and do more hours per gallon of fuel? In the UK, the specification for red diesel is BS 2869, rather than a European specification (as for road diesel - EN590). Back in 1988, this standard covered both road and non-road diesel, but by 1993 the first EN590 standard was introduced covering road diesel.

The most recent version for off-road is BS 2869:2006 "Fuel oils for agricultural, domestic and industrial engines and boilers - Specification". At the time of introduction, the sulphur limit was 2000 mg/kg, but this reduced to 1000 mg/kg at the start of 2008. The specification allows up to 5% bio fuel (FAME) by volume. In Fuels for engine use, the pure FAME must conform to EN 14214, which is the same FAME specification as used for on-road fuels. Sulphur will reduce to 10 mg/kg (same as on-road fuels in EN590) from January 2011, although there is a waiver on this to January 2012 for rail, agriculture and forestry. In the UK, the fuel contains a couple of different markers (the legislated Euro-marker plus some other) to allow for the different taxation. In other European countries, the national specification or supply chain set up may mean that the fuel quality is much more similar to road fuels. I know that in Denmark, the agricultural fuel is the same as the road fuel, with the addition of the Euro-marker to allow for the different taxation.

The question could be divided into two issues. The use of white diesel in a boat, i.e. will it corrode my fuel system and damage rubber hoses, seals and pumps and secondly can white diesel be stored for long periods of time?

White diesel is often called DERV (Diesel Engined Road Vehicle). The diesel that we buy from garage forecourts for diesel cars in the UK is mostly a distillation of crude (fossil fuel oil) that is blended with about 2.5% bio-diesel and kerosene to prevent it from emulsifying, 'waxing' or 'clouding' at low temperatures. Road diesel is filtered to remove impurities such as sulphur and water. The amount of kerosene added by refineries to prevent 'waxing' or 'clouding' is altered depending on the season. This amount tends to not be altered seasonally with red diesel. White diesel tends to only stay in your tank for a few weeks until you need to fill up your car but most boat owners only have to top up every few months. In fact our boats engine is so economical that we only top up twice a year and that's to top up rather than fill up! I could therefore assume that some of the fuel in our tank is several years old. To most people it doesn't matter what the shelf life of white diesel is when run in a car, as you will use it well before it goes off.

The standard of diesel bought in EU countries must comply with BS EN590. The amount of bio diesel blended into road fuel is soon set to rise to about 5% and will be Europe wide and not just for the UK. The percentage is to rise again to at least 7% by 2011. This level is set by the RTFO Renewable Transport Fuel Obligation, which is a EU agreement.

In America service stations have to declare what percentage of bio fuel goes into the fuel. Its measured by a B number. For example B5 is fuel containing 5% bio diesel. B20 is 20% bio and B100 is 100% bio fuel. No such rule applies here.

B100 is supposed to be bio degradable and apparently you can drink it but being bio degradable it would be fair to assume that it will degrade in our tanks?

What is bio diesel? The first working diesel engine ran on peanut oil, which is very much, a type of bio diesel. It is a fuel derived from virgin plant oil such as soy, rape seed or peanut oil or made from waste fats and oils such as left overs from chicken processing factories, fast food fryer oil or lard. It is a methyl ethyl ester oxygenate or fatty acid methyl ester FAME. Top Gear made some to drive a car after buying a field of rape seed. They simply crushed up and filtered the seeds juice. However, it's not as easy as that as they drove the car in summer when the temperature of the car and fuel system was over 20oC. Oils solidify, turn to wax or cloud below 10oC and have to be refined, filtered or impurities and exposed to methanol to be converted into methyl ester. Water, glycerine and food solids are amongst the impurities taken out. Bio diesel is less potent than distillate diesel; its cetane rating is lower and will not produce as much heat when burnt. Fuel consumption would be slightly higher and the boat would not be as fast. However, the small percentages used in fuel would make hardly any difference if the boat were run on DERV.

The arguments to use bio diesel are to me a little overstated. It is said that bio diesel is carbon neutral as the plants that are used to grow it absorb as much CO2 from the atmosphere as the amount of CO2 that is given off when the fuel is burnt. What about the fuel used to process and transport it? And would the fields that were used to grow the bio crop not be used for growing plants anyway? Would we not have to transport food from out of the area that could have been grown where the bio fuel crop was grown?

Will DERV last as well in your tank? Probably just as well as red diesel as such small amounts of bio diesel are blended into it and also because the fuel from the petrol station is likely to be newer as more fuel is purchased from them. Red diesel can hang around for a while, especially over winter months if the fuel is bought from a recreational marina supply. I've bought dirty red diesel before and had to change fuel filters very often after they have got clogged up. My diesel car has done 129,000 miles since I bought it but I have never changed the fuel filter since the warrantee expired years ago and I started to service it myself. Never had an issue with garage fuel but had issues with red diesel on several occasions.

Will DERV damage our boats fuel lines, tank and lift pump? Probably not? 'Earthrace' travelled around the world on 100% bio fuel and had no major breakdowns but did need to change both fuel pumps once. You are probably not going to do 25,000 miles in a Westerly Konsort under engine alone so there is not a lot to worry about.

You need to check with your boat engine manufacturer to see if they approve of bio diesel. Yanmar accept that bio diesel is used in its engines and find this acceptable as long as no more than 5% is used. Petter Lister have bought out a new small marine engine called the Alpha that can run on B100 diesel Most small marine diesel engines are marinised industrial motors which must be able to run reliably on any grade of diesel and have to put up with harsh treatment.

Engine manufacturers have been aware of the impending legislation, which was mostly US driven, meaning that they began to use bio safe compounds in fuel pumps and tank seals as long ago as 1990.

Boat owners will not have a problem if the yacht was built after say 1993. You might have a problem if your vessel is older but you would probably be thinking about replacing the fuel pump, tank, fuel hoses and filters by now anyway, if you haven't already done so? Bio diesel will oxidise in your tank and absorb water. In high concentrations it can degrade natural rubber seals and some plastics.

But it looks as if red diesel will still be available so perhaps no need to worry. This is what the RYA state on their website: 'As of 1 November 2008 red diesel will still be available at the waterside but recreational boaters will pay the full rate of duty when purchasing fuel for the purposes of propulsion. Red diesel used for domestic purposes such as heating and generators will continue to be at the reduced rate of duty.'

The following is advice given out on a fact sheet by Exxon Mobil (Esso)

Under normal storage conditions gas oil and kerosene should be expected to stay in a useable condition for at least 12 months at a temperature of 20 degrees C but only if good housekeeping is maintained.

Fuel stability can be affected by:
Metal contamination: Zinc (galvanised pipes and fittings) and copper rapidly speed the process of gum and deposit formation as well as discolouration of fuel and coking of burners. These metals and alloys containing them should be avoided. Dirt can also introduce these metals
Water: Large amounts of fungi and bacteria can only grow if water is present. These can block filters but also produce organic acids that can destabilise the fuel forming gums and coke when burned and also can cause corrosion
Heat: High temperatures stress the fuel and can cause the fuel to prematurely age - discolouring the fuel and encouraging gum and deposit formation. Again this may cause coking of burners.
To ensure that fuel stays in good condition it is essential that the fuel is well looked after through good housekeeping and the elimination of problem metal components.
If possible: Check water is not present in storage tanks; Ensure storage tanks have a way of draining water; If water is present remove if possible; Ensure that copper and zinc components are not used where they will come into contact with fuel; Empty and clean tanks periodically to prevent sediment and water build up; Where fuel will be stored for a long period, purchase winter grade stocks so that waxing will not occur in cold conditions; Where possible keep tanks full to reduce the build up of water from condensation.

I would like to thank Richard Stradling of Shell Global Solutions for his advice and help when writing this article. I would also like to thank Exxon Mobil's press office and RK Marine Ltd.

Nick Vass B,Sc MIIMS DipMarSur Marine Surveyor