Diesel Bug

Diesel Bug like boat toilet types seems to preoccupy boaters. 

There are certain conditions that need to be in place for diesel bug to occur. Whenever water is mixed in with diesel it provided the conditions for the bug to flourish and grow. Water can get into a diesel holding tank through fuel contamination, condensation and the use of biofuel. Because boats sit in a cold environment, there is more opportunity for condensation to occur within the tank. Diesel bug is the bacterial contamination of the fuel. Most forms of diesel bug require water to reproduce and grow and as soon as the smallest amount of water is present, the bacteria can reproduce rapidly. Diesel bug can produce thick, slimy grunge which can clog up fuel line filters.

Diesel bug is the generic name used for contamination of the fuel. There are a number of different types bacteria and yeasts that can contaminate fuel. Most forms of diesel bug require water to reproduce and grow As soon as water is present, the bacteria can reproduce. Diesel bug can give thick, slimy by-products which can clog up components of the engine. So, water contamination in diesel is something you really want to avoid if you can.

Diesel also deteriorates over time, so it makes good sense to purchase fuel from places that have a high turnover of fuel. (I make the assumption that low diesel base prices will attract more boaters to fill up. Hire fleet boatyards will also have a high volume use) How quickly the diesel is consumed also plays a significant part. Diesel bug is a relatively unknown problem in a vehicle used on the road. This is because it has a small tank and a much higher consumption rate. The tank being quickly consumed and refilled before any water content can settle out. Contrast this with a diesel tank on a boat which can hold hundreds of litres of fuel. (my tank according to the handbook holds a significant investment of 350 litres) The fuel is therefore consumed much more slowly. This length of time provides the bug with an opportune chance to develop.

Red diesel has recently changed consistency and it now contains in addition to the usual mixture a percentage of biofuel. In most cases, biodiesel is compatible with diesel engines constructed in the mid 1990's onwards. Biodiesel is the most common fuel available. It is produced from oils or fats using transesterification and is a liquid similar in composition to fossil/mineral diesel. Chemically, it consists mostly of fatty acid methylesters. Components used for creating biodiesel include animal fats and vegetable oils made from soy, rapeseed,  mustard, flax, sunflower, hemp and the controversial palm oil grown by slash and burn of natural forest in some parts of the world. In many European countries, a 5% bio-diesel blend is widely used.

There is a second minor problem that is created in the short term by using biofuel mixtures. Biodiesel is a mild solvent and will remove over time any built up residues deposited through the previous use of mineral diesel. Therefore until the residues are flushed out over time, diesel filters may need to be replaced more frequently. Biofuel also has its good points as it will clean the engine combustion chamber of carbon deposits, helping to maintain efficiency.

Home processing of vegetable oil for use as cheap fuel is becoming more common. Used chip shop frying oil is increasingly being processed into biodiesel. I would not put any diesel into my boat tank unless I was sure of its provenance. Cheap diesel through canal side deliveries in cans always seems to be a risky option to me so I always avoid it. 

I have used for some time 'Marine 16 diesel bug treatment' as a preventative treatment. I purchase it in 100 mills bottles. I pour a cap full into the diesel tank prior to filling up with fuel.  It seems to work for me as I have not seen any significant build up of sludge or crud in the diesel water trap or fuel filter.

I have also made another small change now that biofuel is added into red diesel. I also use an additive which will improve the performance of the fuel. There have been a significant amount of research done in biofuel mixtures -v- mineral diesel. Many articles have been written about these topics. The consensus seems to be that there is some benefit to be gained through performance from using an additive. I am testing one for myself though I can't claim over the time I have used it, to have noticed any particular improvement.

Warning: You may see advertisements for magnetic in-line devices, which are said to be a tested and proven way to protect engines against microbial contamination. If you can kill bugs with static magnets, how come the Earth's natural magnetic field has failed so far. This is another kind of biofuel and it's called - snake oil.

There are also over the counter chemical additive treatments available for removing water from diesel. A check in your local car spares emporium or a search on line should find a suitable product. There are also water absorption granules available in a long thin sock that is placed into the tank through the filler. It is withdrawn in the same way. A search on line should find a suitable product.

Fuel tank cleaning and diesel polishing treatments available. Like cassette or pump-out it depends on your needs. If you have a heavily contaminated fuel tank - it would make a good start to improving the situation. If you have a mild contamination of water or bug. I think I would use the chemical options and change the filters on a regular schedule.   

Bad things to do include:

• Cheap diesel purchased through canal side deliveries in cans, always seems to be a risky option to me so I always avoid it.
• Purchase diesel through low turnover outlets.

Good things to do include:

• Keeping the diesel tank as full of fuel as possible in winter to help cut down on surfaces where condensation can build-up.
• Use a good diesel bug additive to the fuel whenever you fill up as a preventative measure.
• Drain the diesel line water trap a couple of times a year.
• Change diesel line fuel filter cartridge a couple of times a year.