How to save money on fuel

What works, ranked

Most fuel-saving advice mixes things worth pounds with things worth pennies. In rough order of what they are actually worth to a typical driver over a year:

1. Choosing a cheaper forecourt — worth hundreds of pounds a year.
2. Motorway avoidance for fuel stops — worth £5–£10 per fill if you drive long distances.
3. Moderating motorway speed — worth around 10% of your fuel spend.
4. Tyre pressures and removing dead weight or roof bars — worth a few percent.
5. Smoother acceleration and anticipation — worth a few percent, and free.
6. Loyalty schemes and cashback — worth 1–2p a litre, and only if they do not divert you from a cheaper forecourt.

1. Choose the forecourt — this is the big one

Right now the cheapest forecourt in Great Britain is charging 158.9p and the most expensive 203.0p. Nobody is choosing between those two extremes in practice, but the spread within a single town is routinely 8–12p a litre, which is £4–£7 on a 55-litre tank, every single time you fill.

Two reliable rules cover most of it. Supermarket forecourts average 4.0p a litre less than branded and independent ones (and the fuel is held to the same standard). And motorway services are the most expensive fuel you can buy (worth leaving the motorway for).

Beyond those rules, it is worth actually checking. Find your town's current prices, or use the live map to see everything around you ranked. The habit that saves the most money is deciding where to fill before the gauge gets low enough to remove the choice.

2. Fill at the right time

The old folklore about particular days of the week does not survive contact with the data. What is real is the lag: when wholesale prices fall, retailers pass the drop on slowly and at different speeds, so for a week or two afterwards the variation between nearby forecourts widens considerably. That is when checking pays most.

The practical version of this is to watch specific stations rather than the calendar. Save the three or four forecourts you would realistically use in the CheapestFuel app, turn on price-drop alerts, and fill when one of them moves. You get the benefit of the lag without having to check anything.

The one timing rule that does hold: do not run habitually low. A near-empty tank removes your ability to wait for a good price, and forces you into whatever forecourt is nearest.

3. Driving technique

Worth real money on long journeys, and nothing at all on short ones.

• Speed. Aerodynamic drag rises with the square of speed, so the cost of going faster accelerates. Dropping from 80 to 70mph typically cuts consumption 10–15%. Most cars are at their best between 45 and 55mph.
• Anticipation. Every time you brake you are converting fuel you have already bought into heat. Reading further ahead and lifting off earlier is the single most effective technique change.
• Air conditioning. Worth a few percent in town. At motorway speed, using it costs less than the drag penalty of open windows — so close the windows and leave it on.
• Idling. Modern engines use no fuel on the overrun and restart cheaply. If you are stopped for more than about a minute, switching off saves fuel.

4. The car itself

• Tyre pressures. Under-inflated tyres increase rolling resistance. Checking monthly is worth 1–3% and also makes the tyres last longer.
• Roof bars and boxes. A roof box can cost 10–20% at motorway speed. Take it off when you are not using it — this is one of the larger easy wins.
• Dead weight. Worth less than people think: 50kg of clutter costs roughly 1–2%. Worth clearing, but not worth obsessing over.
• Servicing. A clogged air filter, worn plugs or the wrong oil grade all cost a few percent. Routine servicing pays for a fraction of itself here.

Myths worth ignoring

• "Fill up in the morning when fuel is denser." Underground tanks barely change temperature over a day, and the effect would be a fraction of a percent if they did.
• "Half-fill the tank to save weight." The weight saving is trivial and it costs you the flexibility to fill when you find a good price.
• "Supermarket fuel damages your engine." All UK road fuel meets the same British Standard — covered in full here.
• "Premium fuel improves economy in any car." Only if your engine is tuned to exploit the higher octane. See E10 vs E5.
• "Coasting in neutral saves fuel." It does not — modern engines cut fuel entirely when you lift off in gear — and it reduces your control of the car.