The sulphur content of diesel fuel and its relationship with particulate emissions from diesel engines

Report no. 90/54: This report gives the results of a research programme to investigate the influence of diesel fuel sulphur content on diesel engine exhaust particulate emissions. A representative range of current light-duty vehicles (nine) and heavy-duty engines (four) were tested using European test procedures with four fuels of 0.31, 0.22, 0.12 and 0.055% wt sulphur.

The test fuels were produced by progressively desulphurizing the base fuel, avoiding changes in other fuel quality variables which may have influenced the emissions results. The study found a consistent, but small influence of diesel fuel sulphur on the mass of particulate emissions from the light-duty vehicles: exhaust particulates declined about 7% as fuel sulphur content reduced from 0.3 to 0.05% wt.

For the heavy-duty engines, there was no consistent trend linking reducing particulate levels with reducing fuel sulphur content. This finding differs from the trends found in some US studies. However, those studies used sulphur doped fuels, an artificial situation considered not representative of refining practice in the production of low sulphur fuels.