The sulphur content of diesel is being reduced to no more than 50 ppm (parts per million), down from today's 500 ppm. The new lower sulphur diesel will be introduced progressively from September 2005 and from 1 January 2006 it will be the only diesel available. The move to lower sulphur diesel is a result of changes under the Petroleum Products Specifications Regulations 2002, which define the legal standards for petrol and diesel.

Sulphur in diesel can increase the amount of very tiny particles (called particulates) that vehicles emit. Particulates have been linked to health problems, in particular respiratory conditions. Lowering the sulphur levels in diesel can directly reduce particulate emissions from diesel vehicles. Lowering the sulphur levels in diesel also facilitates the importation of the latest clean diesel vehicles featuring advanced emissions control technologies.

Whilst the reduction in sulphur level is the most significant change being made to diesel, minimum cetane index (burning quality) is also being improved. Lubricity will continue to meet the current specifications for diesel.

Will This Affect All Diesel Vehicles?

Well maintained and newer diesel engines are unlikely to be affected by the new lower sulphur diesel fuel. Older or poorly maintained diesel engines may be affected. This is because the process used to lower sulphur levels in diesel may also lower levels of specific compounds - aromatics - in the fuel.

As diesel systems age they may leak for a variety of reasons and replacing injector pump seals is part of routine maintenance. In some older diesel engines, fuel injection pump seals may be affected by the levels of aromatics in the diesel - swelling when levels are increased and shrinking when levels decrease. The combination of seal shrinking resulting from seal ageing and low aromatics diesel could result in leaks in one or more of the fuel injector pump seals.

Overseas and domestic experience suggests that the seals most susceptible are Nitrile Butadiene Rubber (NBR) seals in older VE rotary fuel injector pumps made by Denso or Zexel that haven't been maintained for six or more years (but other pumps could also be affected). More specifically, older (at least 6 years) cover seals and throttle shaft O-ring seals may be affected. Generally these pumps can be found in pre-1995 Japanese light duty diesel vehicles.

What Should Mechanics Do?

A routine vehicle service should include a visual check of the exterior of the fuel injection pump and this should expose any actual leaks.

Lower sulphur diesel will start being supplied from September 2005 onwards. From this time, particularly in the case of older diesel vehicles, you should ask your customers who own diesel vehicles to regularly check for:

Any diesel pooling under the vehicle,
Moisture or wetness at the bottom of the engine,
Changes in engine exhaust (e.g. a smoky exhaust),
Any unusual smell of diesel when using the vehicle, or
Decreases in the fuel efficiency of the vehicle.

If any of these signs are observed, the fuel injection pump should be checked.

Owners of pre-1995 diesel vehicles with a type VE fuel injector pump may wish to consider a maintenance overhaul and seal replacement before lower sulphur diesel is introduced, to avoid unplanned downtime.

Although the composition of the seals (i.e. NBR rubber) is related to seal swell and seal failures due to the introduction of low aromatics diesel (i.e. lower sulphur diesel) it does not necessarily follow that seals of different composition should be used for replacements. This is because replacement seals should meet the manufacturer's specifications and seals of this type might only be available in the older type materials. Failure to use the correct OEM recommended seals can result in premature seal failure.

For More Information

Call free 0508 33 55 33 [this number is no longer active]
Visit Lower Sulphur Diesel

Technical advice was provided by the Motor Trade Association and the Association of Australasian Diesel Specialists.

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Printed: 26/11/2009

Information for Anyone Servicing Diesel Vehicles

Contents

What's Happening to Diesel and Why?

Will This Affect All Diesel Vehicles?

What Should Mechanics Do?

For More Information