The price of a litre of unleaded in Britain swings about 15p across a single town on any given morning — roughly £8 on a 55-litre tank, paid or saved depending on which forecourt you happen to pull into. Almost nobody checks, because petrol feels like a fixed price. It isn't. It's one of the most variable things you buy each week.

Here's how to stop overpaying.

The app that does the work

PetrolPrices is the one worth installing. It pulls daily prices from ~8,000 UK forecourts, sorts by distance, and shows you the cheapest within a radius you set. Free, with an optional paid tier you don't need.

  • What it saves: typically 5–15p a litre versus the nearest station, by steering you to the cheapest one on your route rather than the one you can see.
  • The trick: check it before you're on empty. The cheapest station is rarely the one you panic-stop at.

Waze also surfaces fuel prices along your route and is free — handy if you're already navigating with it.

Supermarkets beat the motorway, every time

The hierarchy of UK fuel prices is consistent:

  1. Supermarkets (Asda, Morrisons, Tesco, Sainsbury's) — almost always cheapest. Asda historically sets the floor; the others track it.
  2. Big-brand forecourts (Shell, BP, Esso) — a few pence more, more places.
  3. Motorway services — 10–20p a litre more than a supermarket two miles off the junction. A full tank can cost £8–£12 extra for the privilege of not leaving the M-road.

The rule writes itself: never fill up on the motorway unless the warning light is genuinely on. Junctions almost always have a supermarket within a couple of miles.

The loyalty schemes that actually pay

  • Tesco Clubcard and Nectar (Sainsbury's) both give points on fuel, and run periodic fuel-saver promotions.
  • Asda doesn't do points but tends to win on raw price.
  • Some banks and cashback cards still pay 0.25–1% back on fuel — worth routing the spend through one.

Don't drive out of your way to chase points. The distance burns the saving.

The fuel-saving myths worth dropping

  • "Premium fuel cleans your engine and saves money." For an ordinary car, no. Stick to standard unleaded unless the manufacturer specifies otherwise.
  • "Fill up early morning when it's cold and fuel is denser." The temperature difference at an underground UK tank is negligible. A myth.
  • "Keep the tank half full to save weight." The fuel weight saving is trivial against the extra trips. Fill up properly at the cheapest place.

What does save fuel: smooth driving, correct tyre pressure, and not carrying a roof box you forgot about. Aggressive acceleration can cost 20%+ in real economy.

The honest maths

A driver doing 10,000 miles a year in a 45mpg car burns roughly 1,000 litres. Shaving 10p a litre by using the app and avoiding motorway forecourts is £100 a year — for the cost of thirty seconds before each fill-up.

The petrol price isn't fixed. You just have to look.