The methodology for the destructive testing of cartridge filters has been based on experience from the hydraulic oil industry. Accordingly, considerable misunderstanding and confusion still remain concerning both the methods and the techniques involved in filter testing, and in the interpretation of the results produced by these tests. Part 1 of the paper discussed the various types of filter test system that are available, and stressed the need for the development of standard, well defined test methods In order to enhance communication and understanding within the industry. The present paper highlights some of the problems inherent in the use of the dynamic efficiency filter test system, and makes some recommendations aimed at improving the accuracy and operation of these systems.