November 2013

November 2013

Welcome to the great diesel debate!

A number of letters in recent issues of Leisure Wheels have opened a can of worms, sparked debate and produced conflicting opinions. At the heart of the matter is diesel fuel, sulphur – or the lack of it – and two-stroke oil.

When it comes to matters mechanical and technical, we at Leisure Wheels are seriously disadvantaged. We leave it to the boffins to explain these matters to us in layman’s terms, and the diesel debate has often left us scratching our heads in bewilderment.

Those of us growing a little long in the tooth remember the diesel trucks that criss-crossed the nation spewing out great dollops of sulphur-laden smoke. And for those who are as technically/ mechanically disadvantaged as we are, sulphur is added to diesel fuel to produce lubricity – which is essential in diesel fuel to prevent damage to fuel pumps and other components.

Green and environmental issues worldwide have brought about a revolution in diesel engine technology. Petroleum refiners have been forced to meet the demands of diesel emission standards throughout the world and are now producing Ultra Low Sulphur Diesel (ULSD) or S15 in the US.

Locally, the cleanest diesel available at forecourts is S50 – or 50ppm (50 parts of sulphur per million) and will phase out Low Sulphur Diesel (LSD), or 500ppm. The implementation of emission standards worldwide has revolutionised diesel engine technology, and the new engines are powerful and efficient and reduce soot and nitrogen oxide emissions by around 90%.

So far so good. But there is one problem. Current diesel engines are designed to run on 50ppm – but what about those manufactured up to 2007?

The older engines were designed to run on ordinary diesel and could even cope with 3000ppm diesel, which has a higher lubricity which protects fuel pumps and injectors from premature wear and tear. It is here that two-stroke oil enters the debate.

There is a growing number of diesel vehicle owners who advocate adding a small amount of two-stroke oil to LSD with every tank full, or at varying intervals. But there is also a school of thought that points out that if additives work, why don’t fuel companies add these at source? Cost could definitely be a factor.

Fuel leaving South African refineries contains additives and is generally of a high standard and conforms to European and local specifications. Problems can arise, however, in the course of a supply chain that includes road and rail tankers delivering fuel to depots which pass it on to garage forecourts, bulk users and wholesalers.

There is also a criminal aspect to the perception that South African diesel is “dirty” or of poor quality. Many unscrupulous operators – and they are a growing band in all forms of South African daily life – who blend paraffin with diesel fuel.

Paraffin has no lubricity whatsoever. Adding it to diesel reduces the lubricity of the fuel, but a few extra shillings in the back pocket provides an incentive for the malpractice.

There is another interesting side to the diesel debate that has also produced conflicting views. Advocates of adding a little two-stroke oil to 50ppm point to better fuel consumption, while those who follow the “don’t tamper with fuel” school of thought reckon this is a myth.

US Diesel Power magazine recently put this to the test and to obtain baseline figures, the magazine ran up mileage using straight diesel. They then repeated the exercise with a two-stroke additive and recorded a 7% improvement in fuel consumption.

Whether or not you are a supporter of adding two-stroke oil to low sulphur diesel is a matter of “you pay your money and you take your choice”. We do, however, know of one long-time diesel owner who has been adding 200ml of two-stroke oil to every tank of fuel with no problems.

But the diesel debate is set to become irrelevant with the announcement that the Department of Energy has set October 2015 as the date from which fuel producers will have to blend petrol and diesel with biofuels. Producers will have to blend a minimum 5% biodiesel in diesel and between 2% and 10% bioethenol in petrol.

Synthetic additives will continue to play a role in the immediate future, but because it is vegetable oil based, biodiesel is free of sulphur and has a high lubricity factor. These are qualities that make it ideal for blending with LSD and ending the diesel debate