A fuel additive iron salt composition effective in improving the operation
of diesel engine particulate traps when added to a diesel fuel so as to
provide 1-25 ppm iron in the fuel which comprises an oil soluble or oil
dispersible neutral or overbased iron salt of an acidic organic compound,
50-99 mole % of the total iron present in the composition being in the
ferric form, the balance being the ferrous form.