Many of the plug and socket pairs cover a lot of countries. The handy map below shows what regions use what (although Thailand’s type O seems to be absent; you’ll find A, B, C, F, and O there).

Spark plugs are an integral part of your engine, but they need to be replaced every so often. We'll tell you how to find out and what socket size you'll need.

Side view of a typical BS1363 plug, showing the longer earth pin and insulated live and neutral pins. The BS1363 socket has three rectangular receptacles for pins.

I've had a few cars where it would be next to impossible to use regular sockets to get spark plugs changed. My V-10-powered M5 and V-12-powered 850i projects come to mind, as they had especially ...