Turbocharged engines are more exacting than naturally aspirated engines both as regards lubricating oils and engine main components - particularly crankshaft and rod bearings - since they have to cope with the increased loads arising from higher combustion pressures. These problems can be partly solved by improved oil filtration in the lubrication circuit. An effective solution is the so called double filtration.The double filtration filter, described in this paper, is composed of two sections housed in one standard easy-change cartridge. Each section has a specific function: fine filtration in the by-pass section and coarse filtration in the full-flow section. Structure of filter, filtration characteristics and engine test results are described here. Further possible developments are also mentioned.