Abstract: An air filter condition indicating device particularly adapted for use with an air filter positioned in an air flow path, such as in an air induction system of an internal combustion engine for continuously sensing and indicating flow condition of an air filter in the air induction system. The disclosed device includes a transparent tubular member having liquid therein and arranged in a generally U-shaped path with a first leg thereof positioned adjacent an indicia member and adjacent an observation aperture in one wall of a gauge housing. A first flow member communicates between an upstream side of the filter or an air intake portion of the air induction system and an upper end portion of the first leg of the tubular member.