Cheapest petrol London: today’s 20 lowest prices

The ranking uses the pump prices fuel retailers publish under the UK's open fuel price scheme, filtered to Greater London and sorted on unleaded E10 pence per litre. The top twenty are shown because beyond that the differences are small enough to be wiped out by the drive.

Coverage is limited to retailers who publish data, so this is the cheapest petrol we can verify rather than the cheapest petrol that exists. A local independent could undercut the whole list without ever appearing on it. Prices are also a snapshot from the last published file, so the board on the forecourt is always the authority.

Supermarket sites dominate the list most weeks, and outer boroughs generally beat inner ones because land costs and forecourt throughput differ. That is the useful pattern: rather than chasing today's single cheapest pump, note which station within a couple of miles of your normal route keeps appearing here.

The saving on a 50-litre fill at 3p per litre is £1.50. A cross-borough detour of eight miles in a typical car burns most of that in fuel alone, and costs you half an hour of a London evening. Add a chargeable trip into the central zone and the maths inverts completely: £18 of Congestion Charge, or £12.50 of Ultra Low Emission Zone charge for a non-compliant vehicle, dwarfs any pump difference.

Two habits work better than bargain-hunting. Fill before the tank drops below a quarter, so you are never forced into whatever station you can reach; and keep tyres at the pressure on the door plate, because underinflation costs more over a month than the price gap between two forecourts.

The same logic applies to washing. A cheap forecourt wash looks like the saving until you count the drive there, the queue and the drive back. A mobile car wash in London happens where the car is already parked, at a fixed price from £75, with before-and-after photos on the booking.