When using a new filter, dust particles first settle on the fibers of the filter. As contamination increases, the thickness of this dust layer increases and causes a decrease in the pore volume. This leads to the increase in pressure difference. This increase in pressure difference is a typical phenomenon in depth filtration. The pressure difference rapidly increases when the pore volume gets exhausted. When it reaches a specified value by the manufacturer, the filter should be replaced. While studying this process it is found that there is a new parameter that affects the performance of engine pleated air filter, which is the efficiency of the effective filtration area.The efficiency of the effective filtration area (ηeff) is defined as the ratio between the effective filtration area and the total geometric filtration area. The effective filtration area is found to decrease with the increase in temperature, specific dust and flow rate.