Radium Engineering Dual Catch Can Kit 2015-18 Focus ST Fluid Lock - 20-0358-FLOVERVIEW The catch can draws out oil and water condensation from the crankcase gasses that would otherwise be drawn into the intake manifold. This prevents oil buildup in the intake, intercooler system walls, throttle body, and intake manifold. This effectively raises the octane, can increase engine performance from cleaner inlet air, and can lower hydrocarbon emissions. The closed system prevents unwanted oil vapors from entering into the cabin.