When and where to fill up for cheapest fuel
Fuel prices at UK forecourts aren't fixed. They shift through the week and vary significantly by location type. Choosing when and where to fill up can save a typical driver 5–10p per litre compared to filling up at random, adding up to £50–100 per year on a normal fill-up pattern.
The day-of-week effect
UK retail fuel prices follow a loose cycle tied to wholesale movements and competitive retail dynamics. Data from the RAC and CMA consistently shows that Monday and Tuesday tend to have the lowest average pump prices, while Thursday, Friday and Saturday are typically the most expensive. Retailers often raise prices ahead of the weekend when demand is highest and consumers are less price-sensitive.
The pattern isn't consistent across all areas. Competitive markets with multiple supermarkets may show less variation. But the general principle holds: if you have flexibility, filling up on Monday or Tuesday rather than Friday is usually cheaper.
Where to fill up: station type matters most
The choice of station type has a far bigger impact on price than timing. Supermarket forecourts are consistently the cheapest fuel option, typically 5–10p below branded network stations and 15–20p below motorway services. If there's a Tesco, Asda, Sainsbury's or Morrisons forecourt on your regular route, prioritising it for fill-ups is the single most impactful change most drivers can make.
- Supermarket forecourts: Asda, Tesco, Morrisons, Sainsbury's, consistently cheapest. Often 5–10p/litre below branded network.
- Independent stations: Variable. Some are competitive; others price opportunistically. Always worth checking before assuming.
- Branded forecourts: BP, Shell, Esso, typically mid-market. Brand loyalty programmes can offset some of the premium.
- Motorway services: Avoid unless desperate. 15–22p premium over town prices is common.
Morning vs evening fills: does it matter?
You may have heard that filling up in the morning gets you more fuel because cooler temperatures mean denser liquid. Technically true, but the effect is negligible. Fuel is stored underground in insulated tanks and experiences very little temperature variation. The difference in volume between a morning and afternoon fill is typically well under 0.1%. This tip isn't worth planning your schedule around.
The tank level strategy
Letting your tank run very low before filling creates a forced purchase. You have to stop wherever you are, removing any ability to choose a cheaper station. Consistently keeping the tank above a quarter full gives you flexibility to plan fill-ups at the cheapest station on your route. It also protects your fuel pump: repeatedly drawing from the bottom of the tank can accelerate pump wear.
Check PumpItDown before leaving home to find the cheapest station near your start point. On a 300-mile trip, filling a 60-litre tank at 8p/litre cheaper saves nearly £5, before you've even considered planning fuel stops around cheaper junction exits rather than motorway services.
Real-time price data vs rules of thumb
The day-of-week patterns described above are statistical tendencies based on aggregate data — not reliable daily predictions for any individual station. Any forecourt may contradict the pattern on any given day, depending on local competition, recent wholesale movements, or a manager's pricing decision. The most effective approach is not to rely on timing heuristics at all, but to check live price data before a significant fill-up.
Price tracking services update from actual reported retailer prices every 30 minutes. Spending 30 seconds checking what the nearest stations are charging before you need to stop can save 5–12p per litre compared with filling wherever you happen to be when the warning light appears. On a 60-litre fill, a 12p-per-litre difference is over £7 saved on a single transaction.
The two highest-impact decisions — choosing the right station type (supermarket over branded, branded over motorway services) and checking prices before you need to fill up rather than when you are forced to — deliver far more value than any timing optimisation. The Monday/Tuesday rule is a useful fallback when you have no other information; live price data is always more reliable.
Don't over-optimise: diminishing returns
There is a point at which chasing the cheapest fuel costs more than it saves. Driving 4 miles out of your way to save 8p per litre on a 50-litre fill saves £4, but burns around 0.5 litres of extra fuel worth roughly 70p. The net saving is around £3.30 — real, but modest against the time and inconvenience. Driving 8 miles out of your way produces a similar-sized saving but with a worse ratio.
The sweet spot is a cheaper station that is already on or very close to your regular route. A supermarket forecourt 0.3 miles off your commute that is 8p cheaper is an easy win. One that requires a deliberate detour across town may not be worth the effort. The goal is to make price-awareness a background habit — checking before long journeys, knowing which cheap stations are near your regular routes — rather than optimising every individual fill-up in isolation.