Fog Lights: Guides by Make & Model

Rarely used, easy to forget about until needed. Find your specific model below.

Faults Go Unnoticed Until the Fog Rolls In

Not every trim has them fitted, and faults can sit unnoticed for months. Pick your make and model below for the specifics.

Rear Fog Lights Are Legally Required — Front Ones Aren't

Every car first used in the UK on or after 1 April 1980 must have at least one rear fog light, fitted to the centre or offside (driver's side) of the vehicle — this is a genuine legal requirement, not just an MOT convention. If your car has two rear fog lights, only the offside or centre one is actually tested; a faulty nearside one alone won't fail the MOT since the mandatory minimum is still met. Front fog lights, by contrast, are entirely optional from a legal standpoint — many manufacturers reserve them for higher trims, and a car without them isn't missing anything required by law. The MOT rule here is genuinely trim-dependent: front fog lights only get tested at all if your car was first registered on or after 1 March 2018 and actually has them fitted. On an older car, a non-functioning front fog light won't affect your MOT; on one registered from 2018 onward, it will.

When You're Actually Allowed to Use Them

Under Highway Code Rule 226, front and rear fog lights must only be used when visibility is "seriously reduced" — in practice, when you can't see more than roughly 100 metres ahead, about the length of a football pitch. This isn't guidance; it's a legal requirement under the Road Vehicles Lighting Regulations, and using fog lights outside genuinely poor visibility can result in a fine. The reasoning is practical rather than pedantic: rear fog lights are deliberately far brighter than a standard tail light (traditionally 21 watts versus 5 watts) specifically to cut through fog, but that same brightness dazzles following drivers and can mask your brake lights in normal conditions. You must switch them off as soon as visibility improves — leaving them on out of habit is both an offence and a genuine hazard to drivers behind you.

Bulb Type and Common Failure Patterns

The traditional rear fog light bulb is a P21W (also sold as code 382) — a 21-watt single-contact bayonet bulb producing roughly 460 lumens, typically lasting around 1,000 hours of use. LED equivalents draw a fraction of the power (1–3 watts) for the same or greater visible output, last tens of thousands of hours, and respond faster than a filament bulb — genuinely useful given how quickly following traffic needs to register the light coming on.

If both fog lights on one end of the car have stopped working simultaneously, the most likely cause is a blown fuse or a failed relay rather than two bulbs failing at once — check the fuse box first using your handbook before assuming the worst. If only one light has failed, a blown bulb is by far the most common and cheapest explanation, and blown bulbs account for the large majority of fog light MOT failures — a fix costing a few pounds if caught before your test date. Beyond bulbs, watch for a cracked or discoloured lens (a problem specifically if it changes the light's colour or genuinely reduces output — a rear fog light showing anything other than steady red, or a front one showing anything but white, is an MOT failure regardless of whether the bulb itself works), and a loose or insecure housing, which fails the test even if the light functions perfectly.