Abstract: The invention teaches a diesel fuel filter containing a smoke suppressant, and a method of suppressing smoke in exhaust from a diesel engine. The smoke suppressant is adsorbed onto a strip (3) of polyester sponge or mesh. Six to eight strips (3) are inserted in the gaps between the folds of a pleat of filter paper (2), equidistantly around a round container or canister (1), which houses the filter paper (2). The smoke suppressant is slowly released to a stream of diesel fuel flowing through the filter into the diesel engine for subsequent combustion. The additive-coated strips (3) are designed to last the working life of a diesel fuel filter. There are several embodiments of the invention, depending on the sizes or requirements of diesel engines.