Exocet Guide to Fuel Treatment

Fuel Conditioners

The fuel supply in the UK has become highly variable due to a reduction in the use of sulphur and the introduction of ethanol and bio fuel mixes. As a result there are now many fuel additives on the market to tackle various different issues faced in the marine environment.

Modern Diesel Characteristics

In order to reduce pollution emissions, smog and acid rain, the diesel we now buy is Ultra Low Sulphur Diesel. The reduction in sulphur has in turn reduced the lubricating effect and also the shelf life of diesel considerably. As a result your fuel may require additives.

Problems may include, water pick up, deposits, bug growth, power loss, rough running, engine damage.

FAME – Fatty Acid Methyl Ester is a bio fuel from renewable sources which is added to diesel. Unfortunately it can cause some serious issues in marine environments. Diesel bug is more common, filters are more likely to block and the storage life is reduced.

Diesel Bug is the name given to the micro-organisms, bacteria and moulds that form in diesel and can result in poor performance. They live in water and feed on the by-products created from the degradation of the fuel. Water in diesel is not uncommon and can be the result of contamination or condensation. Diesel will often contain some ethanol as well which attracts water and can add to the problem. By preventing water in your tank you can prevent diesel bug at source.

TIP: When storing diesel fuel over the winter period we always recommend you fill the tank as high as reasonably possible to minimise any air space and condensation this can cause.


  Which additives should I use for my diesel engine?

Each time you fill up your tank we recommend that you add Exocet Marine Fuel Conditioner (50ml to every 200lts fuel), all year round.

In winter we recommend that you also add Fuel Store Plus to the tank to stabilise the fuel if the engine is layed up.

What if I have diesel bug?

Exocet Anti-Bug will kill the bug but the fuel will need to be pumped though a fuel polisher to remove water and other contaminants.

What if my diesel engine lacks power?

Exocet Power Restorer is designed to restore optimum power and remove injector deposits. Treat on power loss or on service.

What if my diesel engine struggles on start up?

Exocet Smart Start is a Cetane booster and has improved ignition qualities, especially in cold weather. It also helps remove deposits from the injectors.

Exocet Fuel Additives

Exocet Marine Fuel Conditioner is a liquid fuel additive formulated to upgrade standard marine gas oil and diesel.

  • An increase in the fuel’s cetane number improves overall combustion efficiency leading to improved emissions quality and reducing the tendency of ‘knock’.
  • An increase in the fuel’s shelf life. Fuel left to stand in a marine environment quickly oxidises with the potential to form deposits in tanks and fuel delivery systems; FAME containing fuels are particularly susceptible to this. The additive inhibits the oxidation tendency and allows for safe, longer term storage.
  • A decrease in the fuel’s lubricity is an unintended consequence of the sulphur removal process from diesel, leading to excessive or premature wear in fuel pumps and injection equipment. Exocet Marine Fuel Conditioner compensates for this to provide trouble-free equipment operation.
  • An increase in the fuel’s resistance to microbial contamination. Marine fuel tanks are prime breeding grounds for all manner of micro-organisms – ‘diesel bugs’. If left unchecked these quickly multiply creating fuel sludge, blocking filters and stopping engines – a major safety concern. Regular use of the additive provides a maintenance dose of fuel biocide.
  • An increase in the fuel’s resistance to water pick-up. Fuel naturally takes-up water and this process is enhanced by an increase in humidity and an increase in FAME content. The results are, at best, a reduction in the energy content of the fuel and, at worst, the creation of fuel-water emulsions. The additive promotes continuous fuel-water separation and will break emulsions giving optimum fuel quality.
  • The inclusion of a combustion catalyst. Combustion catalysts improve the reaction between fuel and air. As a result, more of the available fuel in each combustion cycle is burned, resulting in improved fuel efficiency and, more particularly, a reduction in engine emissions, notably particulates (smoke). Having this component in the additive allows the operator to accommodate a wider range of fuel qualities with increased confidence.

Exocet Fuel Store Plus has been specially formulated to protect fuels and fuel systems where fuel is stored for long periods of time and/or the associated equipment is used infrequently. The product acts to delay the symptoms of fuel ageing and additionally has anti-corrosion and biocide properties.

  • Contains a high dose of antioxidant (anti-ageing) component
  • Delays discolouration, gum/solids formation
  • Maintains the fuel’s ignition quality
  • Extends shelf life of fuels to >12 months
  • Contains a fuel soluble biocide at a maintenance dose
  • Reduces the potential for microbial growth during downtime
  • Contains a biocide to inhibit microbial growth

Modern Petrol Characteristics

Petrol is now supplied with much higher levels of ethanol than before and as a consequence this can attract water into the fuel as well as sludge and other contaminants. If the build-up of sludge and water is not too excessive, the contaminants are mostly burnt off in combustion and so petrol boats do not normally require additives. However to reduce water contamination we recommend that water separating fuel filter be fitted.

The main problem arises when the engine has not been started for 2/3 months or more and the fuel remains in storage, especially in damp and cold conditions. In this instance the carburettor should be drained of fuel and fuel storage additive should be added to stabilise the petrol in the tank and prevent oxidisation of the fuel and components.

Which additives should use for my petrol engine?

In winter we recommend that you also add Exocet Fuel Store Plus to the tank to stabilise the fuel if the engine is laid up.