Catalytic Converter: Just pray you don’t need a new one.

Catalytic Converters (or “cats”) convert the toxic emissions of internal-combustion engines into less toxic ones. The Americans introduced them in 1975 to meet some fairly draconian environmental legislation but they rest of us quickly caught up.

Cats are generally a good thing, although they do use precious metals in the manufacturing process which inevitably has political issues (mining in third-world countries etc.) as they mean cars are much greener.

Petrol engines produce Carbon Monoxide which is a very nasty gas, and Cats convert this to carbon dioxide (make your own mind up there). Cats also reduce particulates and odours from diesel engines.

Catalytic Converters are also very expensive to replace (which you will at some point as they wear out, or because you’ve damaged one driving over a kerb) so always fill with the right fuel. And don’t drive over kerbs…