The diesel will be cleaner, but those older engines will still blow smoke

By JULIE MIDDLETON

The composition of diesel fuel is changing in the next few months - and people with a diesel vehicle made before 1995 are likely to be affected.

The Ministry of Consumer Affairs has announced that from August 1 all diesel suppliers must supply their fuel with average sulphur levels of no more than 500 parts per million.

Diesel engines on the new fuel will produce fewer health-damaging emissions, but older vehicles, especially pre-1995 Korean or Japanese light-duty diesel models, may suffer poor efficiency and a smoky exhaust.

This is because the process used to lower the sulphur may also lower the levels of aromatic compounds. In some older engines, the seals on fuel injector pumps may be affected by the level of aromatics - swelling when levels are increased and shrinking when levels decrease.

The Ministry of Consumer Affairs warns that those with older diesel vehicles should be alert for diesel pooling under the vehicle, moisture at the bottom of the engine, a smoky exhaust and decreases in fuel efficiency. If a seal leak is neglected, more serious engine faults could develop.

With the new fuel already being introduced into the supply pipeline, some vehicles could be showing symptoms already, especially those with VE rotary fuel injector pumps made by Denso or Zexel that have not been well maintained, says the Ministry of Consumer Affairs.

Sulphur levels will drop again in January 2006 when diesel suppliers will have to comply with a standard of 50ppm.