Filter cartridge suitable for engaging in a fuel filter, with all or part of a filter housing, said filter cartridge comprising: - a filter element comprising a first end, a second end, and a substantially annular filter medium extending between the first end and the second end, the filter medium having an inner face that delimits an inner space where filtered fuel circulates; - an additive module comprising: - a liquid additive tank suitable for being brought to a fuel pressure of fuel filtered by the filter medium and which delimits a variable internal volume, the tank having a flexible fluidtight wall making the tank deformable, whereby an identical pressure is maintained between the liquid additive contained in the internal volume and said filtered fuel, - a liquid additive outlet pipe, the liquid additive being suitable for mixing with the filtered fuel flowing in a fuel circulation circuit for an internal combustion engine, characterized in that the additive module comprises an attachment end in contact with the filter element in an assembled state of the filter cartridge, the second end of the filter element being engaged with said attachment end so as to stack and/or nest the filter element and the additive module, whereby the filter element and the additive module define a unit adapted for integral insertion, removably, into a fuel filter housing (2, 3), and in that the additive module comprises a self-sealing external connection designed and arranged to discharge liquid additive from the module in assembled state of the cartridge when the external connection is in a state of sealing engagement with a complementary connecting endpiece belonging to a line which is external to the filter cartridge and which is introduced into the inner space through the first end of the filter element, the external connection comprising the additive liquid outlet pipe for delimiting a liquid additive discharge opening in said engagement state of the external connection and having sealing means for automatically closing the liquid additive outlet pipe in a fluidtight manner when the external connection is in a disengaged state, the attachment end being provided with said external connection, wherein the external connection extends longitudinally between a first end where the liquid additive outlet pipe opens into the internal volume of the additive tank and a second end where the liquid additive outlet pipe opens into the inner space delimited by the filter medium. - a filter element comprising a first end, a second end, and a substantially annular filter medium extending between the first end and the second end, the filter medium having an inner face that delimits an inner space where filtered fuel circulates; - an additive module comprising: - a liquid additive tank suitable for being brought to a fuel pressure of fuel filtered by the filter medium and which delimits a variable internal volume, the tank having a flexible fluidtight wall making the tank deformable, whereby an identical pressure is maintained between the liquid additive contained in the internal volume and said filtered fuel, - a liquid additive outlet pipe, the liquid additive being suitable for mixing with the filtered fuel flowing in a fuel circulation circuit for an internal combustion engine, characterized in that the additive module comprises an attachment end in contact with the filter element in an assembled state of the filter cartridge, the second end of the filter element being engaged with said attachment end so as to stack and/or nest the filter element and the additive module, whereby the filter element and the additive module define a unit adapted for integral insertion, removably, into a fuel filter housing (2, 3), and in that the additive module comprises a self-sealing external connection designed and arranged to discharge liquid additive from the module in assembled state of the cartridge when the external connection is in a state of sealing engagement with a complementary connecting endpiece belonging to a line which is external to the filter cartridge and which is introduced into the inner space through the first end of the filter element, the external connection comprising the additive liquid outlet pipe for delimiting a liquid additive discharge opening in said engagement state of the external connection and having sealing means for automatically closing the liquid additive outlet pipe in a fluidtight manner when the external connection is in a disengaged state, the attachment end being provided with said external connection, wherein the external connection extends longitudinally between a first end where the liquid additive outlet pipe opens into the internal volume of the additive tank and a second end where the liquid additive outlet pipe opens into the inner space delimited by the filter medium. - a liquid additive tank suitable for being brought to a fuel pressure of fuel filtered by the filter medium and which delimits a variable internal volume, the tank having a flexible fluidtight wall making the tank deformable, whereby an identical pressure is maintained between the liquid additive contained in the internal volume and said filtered fuel, - a liquid additive outlet pipe, the liquid additive being suitable for mixing with the filtered fuel flowing in a fuel circulation circuit for an internal combustion engine,