Abstract: An accessory or attachment device for existing or newly manufactured internal combustion engines bleeds incompletely burned combustion products from the engine exhaust upstream from the exhaust manifold and returns or recycles the combustion products through the carburetor to the combustion chambers of the engine where complete burning of the products takes place. Carbon monoxide in the final exhaust from the engine is reduced almost to zero and substantially the full energy present in the hydrocarbon fuel is utilized, rather than being wasted into the atmosphere as occurs in conventional engines. The device subjects the recycled combustion products to violent agitation and comminution before returning them through the carburetor to the engine fuel induction system.