[talkingcars]

Part of the "modern" way of controling vehicle emmisions is to vent the fumes from the crank case back into the inlet and thus into the engine to be burnt.

These fumes have a fine mist of engine oil which collects in the inlet manifold, drips into the airfilter and gums up the VIS motors and flaps.

The catch tank incercepts the oil mist reducing the amount of rubbish going into the inlet etc.