Fuel is changing rapidly. Where hydrocarbon fuel quality was once consistent, now each batch of fuel has varying degrees of quality measured against industry specifications. As refining margins decrease globally, the drive to maximise crude yield increases. This in turn leads to an increase in long chain hydrocarbons shown to reduce fuel quality. Global fuel specifications are also being updated more frequently than ever before in order to gradually reduce our dependence on fossil fuels & greenhouse gas emissions.

By altering the chemical components of fuel combined with new emissions prevention technology, it is then possible to reduce the production of these emissions (Sulphur, Nitrogen & Carbon Oxides) post-combustion. The predominant changes to the components of fuel are a reduction in sulphur content and an increase in bio-derived content such as Bioethanol or FAME (Fatty Acid Methyl Ester), often found in Biodiesel. These changes have a proven depreciatory effect on fuel quality despite the warnings of industry professionals and users. Changes are primarily mandated by local and international legislation through evolving fuel specification changes and engine emissions regulation.

Fuel quality is statistically proven to be deteriorating. Test data shows a direct correlation between key legislative changes and the number of off specification (i.e. poor quality) fuels. For example, in the marine industry, 2013 saw the greatest recorded rise in poor quality delivered fuels with 1 in 4 M.G.O. (Marine Gas Oil/ISO 8217) samples being off specification. A similar pattern has been seen in both road & off-road fuels across Europe. These off-specification fuels, without changing their processing, can only be consistently preserved through the use of fuel treatments.

Poor fuel quality has a detrimental impact on both storage & combustion. These ultimately lead to key problems in organisation operations, including:

  • Increased fuel spend
  • Increased maintenance
  • Reduced operational efficiency
Fuelcare provide a range of services to combat the delterious effect poor fuel quality has on important operations. Fuelcare can provide biocides, detergents, & multifunction additives to keep your fuel quality optimal and your assets running efficiently.

The majority of fuel quality problems can be linked to the most recent changes in fuel specifications: lowering Sulphur content & increasing biologically derived content such as FAME.

Lowering Sulphur Content

The reduction of Sulphur in fuels has been implemented to allow the use of emissions reduction technologies in engines. The side effects to this can be varied:

  • Sulphur inhibits microbial growth in fuel - the less Sulphur present, the more likely organic growth is achieved. This in turn leads to filter blockages (leading to fuel starvation & engine shutdown), fuel pump failure and tank & line corrosion.
  • Poor fuel stability leading to tank sludge and fuel discolouration.
  • Vastly reduced lubricity leading to possible pump system failure & other issues. Processing to remove Sulphur removes other components with natural lubricity.
  • Combustion efficiency - a small but noticeable reduction in fuel economy.

Sulphur content is varied depending on the fuel specification and local legislation. The predominant reduction in Sulphur now makes most road & off-road fuel supplies 'U.L.S.D.' or 'Ultra Low Sulphur Diesel' - i.e. containing less than 10 or 15ppm.

Increasing Biologically Derived Content

The increase in Bio-derived content in your fuel, whilst shown to offset the lubricity issues of reduced Sulphur, has some known side-effects to your fuel quality:

  • Poor oxidation stability (tank sludge).
  • Affinity for water and therefore microbial growth.
  • Poor cold flow properties.
  • Reduced combustion & ignition efficiency.
  • Increased filter blocking tendency.
  • May be corrosive to certain materials.
  • Rubber gaskets, hoses & seals may swell.

Bio-derived content is now found in most fuel specifications to some degree including automotive & marine fuels. Other industries will see an increase in this component before 2020 as fuel regulations change.

Microbiological Growth in Hydrocarbon Fuels

One of the most common issues facing fuel quality is that of microbiological contamination. It is almost impossible to eradicate water and microbiological contamination from fuel storage tanks and systems used for gas oil, derv, kerosene and petroleum spirit. The resultant brown or black slimes and sludge are a major cause of costly tank corrosion, filter blockages, pump failure, and poor performance. Treatment can provide the most effective and economical solution to fuel spoilage.

It is well known that contamination in the form of bacteria or fungal growth exists in most middle distillate fuel oil storage tanks downstream from the refinery. The remedies are less well known. The result of contamination can be simply poor performance of engines or oil burners or, more seriously, partial blockage of fuel lines and fuel filters due to the accumulation of black sludge and slimes in the bottom of the fuel storage tank. The catastrophic failure of the engines or burners, acidic corrosion of fuel pumps, injectors and storage tanks can cause fatal consequences and is certainly expensive.

There are usually high levels of awareness of the cause and solution to microbiological contamination amongst personnel in the oil distribution chain. On the other hand the general public, and service industries engaged in oil burner and engine maintenance are usually unable to diagnose the problem without expert help.

Airborne bacteria and fungi can readily enter fuel tanks through air vents, and multiply very fast in this bottom water phase. These micro-organisms do in fact need the presence of water in order to multiply, but given a very small initial quantity, they can actually produce their own supply of water by feeding off the fuel. This is particularly likely to happen in diesel and gas oil tanks where it is impossible to exclude water altogether. Water enters these tanks by various methods, such as through condensation, rain water or ground water leakage, or even with the fuel delivery.

Microbiological growth will often produce black sludge but the worst type of micro-organisms are the Sulphate reducing bacteria (S.R.B.'s). These produce acidic by-products which can corrode fuel tanks and systems, with the potential to cause severe damage.

There is strong evidence that the incidence of contamination is increasing due to legislative fuel changes. Local weather conditions are often overlooked as the cause of this contamination producing condensation in cold periods followed by rapid growth in following warm periods. Treatment with a fuel biocide is often the only 100% effective way of dealing with microbial fuel contamination. Fuelcare recommend KATHON™ FP 1.5 Fuel Biocide for immediate results.

Fuel Changes How They Affect Operations


Engines designs are changing at breakneck speed. In European road-going machinery the EURO emissions restrictions apply to vehicles (EURO IV/V/VI) leading to a raft of engine changes designed to reduce emissions. Modern fuel injection technologies are the primary method of facilitating compliance with these stringent emission targets. In order to meet these targets, injectors now feature smaller orifices and tighter tolerances.

In addition, newer high pressure fuel injectors (HPFI) or high pressure common rail (HPCR) systems create pressures and temperatures that have never been seen before in engines for example pressures such as 30,000 psi on inlet side of injector and temperatures of 150-200°C or more. Greatly increased pressures (2000 Bar) are therefore required to generate adequate fuel flow through reduced injector dimensions. Diesel Fuel and Biodiesel blends are unstable at these extremes - fuel breaks down and then forms particulates, usually found on the injector nozzle. Injector fouling then causes a range of engineering issues:

  • Filter blocking & a shortened P.M.I. (Preventative Maintenance Interval)
  • Power loss
  • Reduced drivability
  • Economy deficits and an increased fuel spend

Injector fouling is the predominant means of engines reducing power & fuel economy. As the engine runs over time, power loss increases as injectors become saturated by deposits. These deposits originate from a range of sources including temperatures & pressures discussed above, biodiesel components, lube oil adulteration, water & dirt and metallic contamination. Heavy duty engines by means of their fuel specifications and running times often suffer the worst of these issues. As well as the engine performance suffering a range of other problems ensure including fuel tank sludge (by way of diesel return), fuel pump failure (through lost lubricity components) and fuel filter blocking (caused by sludge & gums).

Fuelcare can provide fuel treatments designed for road, off-road & marine engines to counteract these issues. For more information please see our EcoClean™ HSDI & Octamar™ LI-5 Plus pages.

Engine Changes How They Affect Operations