This is the return pipe from the oil cooler to the oil filter housing on E90/E92/E93 M3 produced from 3/2008-2013. It returns oil that has been through the cooler back to the engine. The line is made up of metal pipes and a rubber hose section with crimped fittings that may develop a leak over time.
New o-rings are required. New o-rings are available below.
BMW Fitments:
3 Series
E90 / E91 / E92 / E93 (06-13) > M3