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What's Wrong With Australia's Diesel?

It's well known that the quality and cleanliness of diesel fuel in Australia leaves much to be desired.

Some sources even list the quality of Australian diesel as the worst in the world, and while this may not be true, the fact is that modern diesel engines require fuel that is cleaner than the fuel that is currently available in Australia. There are laws that look at the diesel fuel cleanliness standards, namely the Fuel Standard (Automotive Diesel) Determination 2001 that was replaced with the Fuel Quality Standards (Automotive Diesel) Determination 2019, which came into effect on 1 October 2019. However, while the new standard does make provision for the improvement of several aspects concerning the chemical composition of diesel fuel, some aspects of diesel fuel that have a direct bearing on engine longevity in general and on injection equipment in particular, remain unchanged. 

Water contamination in diesel fuel

Even the cleanest diesel contains at least some dissolved (and sometimes free) water as a result of poor storage, handling, and shipping practices. However, in the case of Australian diesel, the water and sediment content of almost any diesel sample will almost invariably exceed the maximum allowable values by several orders of magnitude. The principal reasons for this are that much of Australia’s diesel is imported from Japan, South Korea, Malaysia, and other Asian countries. In addition, most shipments are stored mainly in Singapore for various lengths of time before being shipped to Australia.

Moreover, since some distribution lines in Australia stretch over several thousand kilometres and involves several transfers between ships, pipelines, road and/or rail tankers, and poorly maintained storage facilities, there is simply no telling exactly where, when, and how much water and other contaminants enter the fuel. Suffice to say that diesel fuel in remote Australian locations is often visibly contaminated with water, dirt, and various other types of sediment.   

Sediment content in diesel fuel

While most sediment in Australian diesel consists of dust, dirt, and rust particles, some types of sediment consist entirely of bacterial colonies that live in the interface between suspended water droplets and diesel molecules. Thus, since it is impossible to treat the entire national distribution network to remove all bacterial colonies, an entire pipeline or sub-distribution network can become infected with various species of microorganisms.

Therefore, should you unknowingly pump infected diesel into your tank, there is a high chance that the bacterial colony will grow and could clog fuel lines, filters, pumps, and even injectors.

Filter blocking tendency

Filter blocking tendency is a measure of how likely it is that diesel fuel will clog filters in the distribution network, or while in use in a vehicle or other application, such as for instance, a stationary generator.

Determining the tendency of diesel (or other fuels) to block filters is a rather involved process, but briefly, the process involved passing 300 ml of the fuel through a specified filter medium. According to the ASTM D2068 and IP 387 standards, the fuel sample must pass through the filter at a constant rate of 20 ml per minute while the pressure difference across the filter is monitored either until the pressure differential reaches 105kPa, or 300 ml of the sample had passed through the filter. If, however, the pressure differential reaches 105 kPa before 300 ml of fuel had passed through the filter, the volume of fuel that did pass through the filter when the pressure differential reached 105 kPa is used to calculate a filter blocking tendency value.

As a practical matter, the lower the obtained value, the cleaner the fuel, but to put the legally required filter blocking tendency value of 2 into some perspective, a filter blocking tendency value of 2 would seem to incorporates a considerable safety margin, but this is in fact, not the case. The reality is that the filter blocking tendency value of a fuel does not take account of the nature of the impurities in a fuel. For instance, while very specific quality standards exist in Australia that should regulate the quality of biodiesel, the fact is that very little, if any quality control is performed on the biodiesel that makes it into diesel/biodiesel blends that are sold in Australia.

Biodiesel Oil Fuel

One of the biggest issues with biodiesel is that incomplete conversion of fats and/or oils in the base feedstock can leave significant amounts of wax-like compounds in a production batch, and if these unconverted fats and/or oils make it into a diesel blend, the end result is clogged fuel lines and/or fuel filters. This issue can be aggravated by low ambient temperatures, which not only causes the unconverted fats to coagulate faster, but also increases the overall viscosity of the diesel fuel blend over wide range of temperatures.

As a general rule, the higher the biodiesel component of a fuel blend is, the higher the chances become of at least some constituents of the blend solidifying at low temperatures. Moreover, if one adds the fact that there may be significant amounts of unconverted fats present in the biodiesel component of the blend, the higher the possibility becomes that some diesel blends may clog fuel filters at temperatures that are well above freezing.   

While all of the above may appear a bit disconcerting considering that, for the most part, Australian petrol does not have these issues, there are ways to avoid at least the worst aspects of Australian diesel fuel. One such way involves the use of aftermarket water traps and pre filters.

Click here to learn more about diesel engines.