A fuel composition contains (a) a medium substantially free of to free of sulphur; (b) a detergent/dispersant additive; and (c) a liquid fuel where the medium substantially free of to free of sulphur is an aliphatic hydrocarbon solvent, and where the aliphatic hydrocarbon solvent is present from at least about 50 wt % to about 100 wt % of the total amount of the medium. The fuel composition is prepared by a process and is useful in a process, where the fuel composition includes a medium that is a hydrocarbon or a nonhydrocarbon or a mixture thereof, to increase the efficiency of an exhaust after-treatment device of an internal combustion engine.