This invention relates to diesel fuels which are useful with diesel engines equipped with exhaust system particulate traps. These fuels contain an effective amount of an organometallic complex to lower the ignition temperature of exhaust particles collected in the trap. The organometallic complex is soluble or stably dispersible in the diesel fuel and is derived from (i) an organic compound containing at least two functional groups attached to a hydrocarbon linkage, and (ii) a metal reactant capable of forming a complex with the organic compound (i), the metal being any metal capable of reducing the ignition temperature of the exhaust particles. The functional groups include .dbd.X, --XR, ##STR1## --CN, --N.dbd.NR and --N.dbd.CR.sub.2 ; wherein X is O or S, R is H or hydrocarbyl, R* is hydrocarbylene or hydrocarbylidene, and a is a number (e.g., zero to about 10). Useful metals include Na, K, Mg, Ca, Sr, Ba, V, Cr, Mo, Fe, Co, Cu, Zn, B, Pb, Sb, and mixtures of two or more thereof. This invention is also directed to methods of operating a diesel engine equipped with an exhaust system particulate trap using the foregoing diesel fuel.