This part of ISO 4548 specifies a multi-pass filtration test with continuous contaminant injection and using the online particle counting method for evaluating the performance of full-flow lubricating oil filters for internal combustion engines. The test procedure determines the contaminant capacity of a filter, its particulate removal characteristics and differential pressure. This test is intended for application to filter elements having a rated flow between 4 l/min and 600 l/min and with an efficiency of less than 99 % at a particle size greater than 10 μm. NOTE Several test flow loops built into one test rig, or several test rigs, would be required to cover the complete flow range of 4 l/min to 600 l/min.