Trapping diesel particulates is effective in reducing both the number and the mass of fine particulate emissions from diesel engines, but unless the accumulated soot can be burned out or regenerated periodically, the vehicle to which the trap is fitted will cease to function after a relatively short time. A programme of work with soot traps using a low treat rate iron-strontium organo-metallic fuel additive to assist and secure regeneration has been carried out. As part of this programme, an advanced specification diesel engine passenger car equipped with a diesel particulate filter (DPF), was operated on roads in the UK for approximately 18 months, during which time the vehicle covered over 50,000 kmAfter completion of 50,000 km on roads, the vehicle was operated on a chassis dynamometer to increase the distance covered with a DPF more rapidly to a final total of 80,000 km.The car was fitted with a simple passive ceramic particulate filter or soot trap, without a heater or other regeneration device. Instead, reliance was placed on the use of a fuel-soluble combination of iron and strontium, delivering 20 mg/kg of metal in the fuel. The fuel sulphur content of approximately 430 mg/kg met European limits at the start of the test in late 1998.The test work comprised emissions testing several times during the trial to monitor the effect of the soot trap and additive on both gaseous and particulate emissions. Regeneration performance was monitored by means of a dedicated on-board data logger, and associated instrumentation. Lubricant oil samples were taken at intervals to monitor the effect of the fuel additive on lubricant properties, and to provide information on engine wear effects. This paper examines the results of the long term test of fuel additive combined with soot trap, which was an effective demonstration of the feasibility of this approach to control diesel particulate emissions.