Measurements with different diesel engines and fuel additives permit a characterisation of the aerosol of a diesel engine under the influence of fuel additives. Combined with chemical analysis and gravimetry a clear picture of the size range and composition of the emitted particles is obtained. Emission factors computed by gravimetry and coulometry correlate well. A correlation is found between the minimum additive concentration needed to induce exhaust particles consisting of additive products, and the elemental carbon emission factor of the engines. It provides information for optimising the exhaust cleaning system.