Abstract: Vehicular emissions are reduced/purified via combustion of the hydrocarbon fuel therefor, e.g., diesel fuel, in the presence of a cerium compound, preferably a cerium (IV) compound, to produce soots having depressed ignition temperatures that contain effective purifying amounts of aggregates of ceric oxide crystallites, the largest particle size dimension of which ranging from 50 .ANG. (5 nanometers) to 10,000 .ANG. (1,000 nanometers) and the crystallite sizes of which, measured by Debye-Scherrer technique, ranging from 50 .ANG. (5 nanometers) to 250 .ANG. (25 nanometers).

Abstract: A method and apparatus for the automatic injection of an additive into the fuel tank of a motor vehicle, from an on-board additive tank in which the quantity of additive to be withdrawn from the additive tank is determined using an on-board computation unit, and the quantity of additive thus determined is injected by pulsed atomization, this atomization being carried out directly into the liquid bulk of the fuel. This pulsed atomization is preferably carried out by controlling a positive-displacement piston, where the number of strokes of the piston which is automatically determined as a function of the quantity of the additive to be withdrawn.