A filter for filtering oil of internal combustion engines comprising: - a filtering chamber adapted to be closed by means of a cover and a slidable shutter arranged within the filtering chamber and adapted to close a bleed channel for the fluid; - a cartridge assembly for filtering liquids having at least one inlet channel and one outlet channel, all of them being contained in said filtering chamber, said cartridge assembly comprising: - a filtering element comprising a first flange, a second flange and a filtering material which is arranged so as to define, within the filtering element, a longitudinal hole communicating with an outlet channel of the filter, said filtering material being held between said first flange and said second flange, said first flange having a first surface connected to the filtering material and a second surface which is opposite to the first surface and comprises removable connection means; and - a drainage component comprising complementary means removably connectable to said connection means of the first flange, wherein said drainage component comprises an open mouth and a closed end which is arranged transversely to a longitudinal axis (Z-Z) of the filtering element and internally to the longitudinal hole, and wherein said drainage component is arranged to constitute, with its closed end, a closing plug for closing the longitudinal hole of the filtering element, in order to avoid leakages and consequent pollution of the filtered fluid by the fluid which is still to be filtered, characterized in that said closed end of the drainage component comes into abutment against the shutter inserted in the longitudinal hole of the filtering element, so as to push the slidable shutter downwards, thus closing the bleed channel of the filter. - a filtering chamber adapted to be closed by means of a cover and a slidable shutter arranged within the filtering chamber and adapted to close a bleed channel for the fluid; - a cartridge assembly for filtering liquids having at least one inlet channel and one outlet channel, all of them being contained in said filtering chamber, said cartridge assembly comprising: - a filtering element comprising a first flange, a second flange and a filtering material which is arranged so as to define, within the filtering element, a longitudinal hole communicating with an outlet channel of the filter, said filtering material being held between said first flange and said second flange, said first flange having a first surface connected to the filtering material and a second surface which is opposite to the first surface and comprises removable connection means; and - a drainage component comprising complementary means removably connectable to said connection means of the first flange, wherein said drainage component comprises an open mouth and a closed end which is arranged transversely to a longitudinal axis (Z-Z) of the filtering element and internally to the longitudinal hole, and wherein said drainage component is arranged to constitute, with its closed end, a closing plug for closing the longitudinal hole of the filtering element, in order to avoid leakages and consequent pollution of the filtered fluid by the fluid which is still to be filtered, characterized in that said closed end of the drainage component comes into abutment against the shutter inserted in the longitudinal hole of the filtering element, so as to push the slidable shutter downwards, thus closing the bleed channel of the filter. - a filtering element comprising a first flange, a second flange and a filtering material which is arranged so as to define, within the filtering element, a longitudinal hole communicating with an outlet channel of the filter, said filtering material being held between said first flange and said second flange, said first flange having a first surface connected to the filtering material and a second surface which is opposite to the first surface and comprises removable connection means; and - a drainage component comprising complementary means removably connectable to said connection means of the first flange, wherein said drainage component comprises an open mouth and a closed end which is arranged transversely to a longitudinal axis (Z-Z) of the filtering element and internally to the longitudinal hole, and wherein said drainage component is arranged to constitute, with its closed end, a closing plug for closing the longitudinal hole of the filtering element, in order to avoid leakages and consequent pollution of the filtered fluid by the fluid which is still to be filtered, characterized in that said closed end of the drainage component comes into abutment against the shutter inserted in the longitudinal hole of the filtering element, so as to push the slidable shutter downwards, thus closing the bleed channel of the filter.