an apparatus for determining hydraulic pressure within a pressure sensing fluid filter assembly includes a pressure - sensing polymer thick film transducer associated with an oil filter assembly . preferably , pressure sensors are provided on both the oil inlet and outlet areas of the filter . the pressure - sensing transducers send signals to a control module , which may compare pressure readouts at the inlet and outlet sides of the filter . based on the pressure in the filter , the on - board sensing system will detect a clogged filter condition , and if necessary , the control module will send a signal to an in - dash display terminal , to indicate that an oil change is needed .