The traditional filter type oil purifier is uneconomical. Because the filter has to be replaced with new one when it is clogged by any external substances such as sludge, etc.
The reason of this replacement is because the damaged filter can not remove carbon and water. But ISP-type purifier promotes the efficiency of engine by using two separated filters to remove sludge(1st filter) and water(2nd filter). Two filters can be segregated from each case to control the contamination of 2nd filter. Also, the filters are reusable by cleaning them and semi-permanent.
In addition, the auto drain system gives more convenient than the past manual operation of draining tank.