Oil catch can is used to remove oil mist/vapour trom engine sump (piston/rings blowby which all diesel engines have ) from entering HPEGR and mixing with exhaust gas fumes to make a sticky crud which blocks inlet manafold,valves,intercooler and HPEGR valve.So well worth fitting to any diesel engine.Search utube to see images of the crud buildup in manufolds etc.The biggest problem fitting one to ducato is finding a suitable space for it under the bonnet.