Catalytic converters work with unleaded gasoline and diesel. Leaded gasoline, however, "poisons" the catalyst with a lead coating that prevents it coming into contact with pollutants.

By how much do they reduce pollution?

By most estimates, catalytic converters fitted inside the exhaust pipe of a gasoline-operated car convert up to 90 % of hydrocarbons (HC), carbon monoxide (CO) and nitrogen oxides (NOx) from the engine into less harmful carbon dioxide (CO2), nitrogen and water vapour. Diesel engines, in addition, emit particulates. The use of a particulate trap, in conjunction with a catalyst, can reduce their mass by 90% and reduce the number of ultra-fine particles by 99%.

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