Liqui Moly 8931 Catalytic-System Cleaner 300 ml.Cleans intake valves and the combustion chamber. Pour additive into the LIQUI MOLY Pump-spray Bottle (part no. 3316). Pump up the pump-spray bottle. Start the engine and spray the additive into the intake tract at short intervals while the engine is at moderate speed (2,000-3,000 rpm).