Costco's petrol stations have a reputation as the cheapest forecourts in the UK. But supermarket petrol is cheap too, and you need a paid membership to fill up at Costco. This post checks the claim against our own daily Costco prices, the government's weekly UK averages and supermarket prices from October 2026. It then works out how many litres a year it takes to cover the membership fee.
Short answer: Yes. On 15 October 2026 our 22 UK Costco petrol stations averaged 166.0p a litre for unleaded and 190.4p for diesel. On 12 October, the government's latest survey date, Costco was 8.7p a litre below the UK average for unleaded and 9.0p for diesel. On 15 October it was about 5–7p below Tesco, Sainsbury's and Morrisons. Against the cheapest Asda near each Costco, the typical gap was 4p. At those gaps, the £42 Gold Star fee pays for itself after roughly 500 to 1,050 litres a year, depending on where you would otherwise fill up.
Is Costco fuel cheaper than the UK average?
Yes, by about 9p a litre for both petrol and diesel. The cleanest comparison is the government's weekly survey of UK pump prices, published by the Department for Energy Security and Net Zero (DESNZ). Its weekly road fuel prices for Monday 12 October 2026 put the UK average at 175.28p a litre for unleaded and 200.04p for diesel.
We compared that with the average of our 22 UK Costco petrol stations on the same day:
The gap was similar a week earlier. On 5 October DESNZ had 174.88p for unleaded and 199.52p for diesel, while Costco averaged 166.85p and 191.72p. That's 8.0p and 7.8p lower.
Costco is cheaper everywhere we track, but the price varies by site. On 15 October, Liverpool had the cheapest Costco unleaded at 161.9p, with Haydock, Leeds and Birmingham at 162.9p. Reading was the dearest at 170.9p. Every Costco on our list was still below the 12 October UK average. For diesel, Edinburgh and Watford were cheapest at 184.9p, and Reading and Southampton dearest at 194.9p. The Costco diesel price page shows today's figure for every site, and our Costco diesel UK guide explains what Premium Diesel is.
Is Costco petrol cheaper than supermarket petrol?
Yes, but the gap is smaller than the gap to the national average. Supermarkets are already among the cheapest places to buy fuel, so they pull the average down.
Every UK forecourt has had to report its prices to the government's Fuel Finder scheme since 2 February 2026, within 30 minutes of any change. That data is published openly, and a number of comparison sites now build retailer averages from it. One of them, Pennr's fuel price index, published these averages on 15 October 2026:
Pennr is a third-party site, not the government, and its own Costco figure (166.9p unleaded from 13 reporting sites) was a little higher than our 22-site average. We haven't checked its supermarket figures against the raw Fuel Finder feed, so treat them as a good guide rather than an exact measurement.
What about Asda?
Asda publishes its own price feed, which we downloaded for 14 October 2026. Across 785 Asda forecourts, the average was 174.86p for unleaded and 199.37p for diesel. That's 8.6p and 8.7p above Costco's average that day (166.22p and 190.63p). The feed covers more sites than Asda has superstores, so it seems to include smaller Asda Express forecourts, which may be why the average is high.
A fairer test is the cheapest Asda near each Costco. We matched 21 of our 22 Costcos with every Asda within 8 km (Aberdeen had none) and compared Costco with the cheapest one on 14 October:
- Costco was cheaper than the cheapest nearby Asda at all 21 sites, for both petrol and diesel.
- The typical (median) gap was 4.0p a litre for unleaded and 3.8p for diesel.
- The range was 3.0p to 10.0p for unleaded and 2.8p to 9.8p for diesel.
So the honest answer is that Costco usually beats the national average by 8–9p a litre, the big supermarket chains by 5–7p, and the cheapest supermarket forecourt in the area by about 4p.
Those comparisons are a snapshot from mid-October 2026, and Costco's own prices change most days.
How many litres pay for a Costco membership?
You need a Costco membership to use the pumps (which memberships work at the pump), so the saving has to cover the fee before fuel puts you ahead. Costco UK's membership page listed these annual fees on 15 October 2026:
Divide the fee by the saving per litre and you get the break-even volume:
A worked example
Take a driver who covers 10,000 miles a year in a car that does 45 miles per gallon. That's about 222 UK gallons, or roughly 1,010 litres a year (one UK gallon is 4.546 litres).
- If they usually fill up at an average-priced forecourt, Costco saves about 8.7p × 1,010 litres = £88 a year. Take off the £42 Gold Star fee and they're £46 ahead.
- If they would otherwise use a Tesco, Sainsbury's or Morrisons, the saving is about 5.6p × 1,010 = £57. That's £15 ahead after the fee.
- If they already use the cheapest Asda in town, the saving is about 4.0p × 1,010 = £40. That's roughly the cost of the membership.
Per tank, the numbers are small but they add up. On a 55-litre fill, 8.7p a litre is £4.79. 4p a litre is £2.20.
Three things change the maths:
- Shopping inside. Most people join Costco for the warehouse, not the pumps. If you'd pay the fee anyway, every litre is pure saving.
- The drive. There are only 22 UK Costco petrol stations. A 10-mile round trip in that 45mpg car uses about 1 litre of fuel, costing about £1.70. That wipes out the 4p-a-litre saving on a 40-litre fill. Use the Costco near me finder to see how far away your nearest one is.
- Opening hours. No UK Costco forecourt is open 24 hours. Check Costco petrol opening times before you plan a trip, and see why the pumps keep different hours from the warehouse.
Don't add the Executive 2% reward to your fuel savings. Costco UK's member conditions list "Fuel or EV Charging" among the purchases that don't earn it, as in the US and Canada (see Costco membership and the pump).
Why is Costco fuel so cheap?
Costco treats fuel as a reason to visit the warehouse, not as a profit centre. Its fiscal 2025 annual report, which covers the UK alongside its other countries, says: "We believe our gasoline business enhances traffic in our warehouses; it generally has a lower gross margin percentage and lower SG&A expense relative to our non-gasoline businesses."
In practice that means:
- Thin margins by design. Costco takes a smaller cut per litre because fuel customers keep coming back and spend money inside. Costco doesn't publish a UK fuel profit, so we can't say whether it ever sells below cost. "Low margin" is accurate. "Loss leader" can't be proven from what it publishes.
- Membership fees carry the profit. Members pay up front every year, so Costco doesn't need to make much on each litre.
- High volume. Costco sites have many pumps and serve a large catchment, so fixed costs are spread over more litres.
- Few products. Costco forecourts sell three fuels: unleaded, super unleaded (Costco's Premium Unleaded 97) and diesel. They are run as fuel stops, not as convenience shops with a till queue to staff.
Compare that with the wider market. In its December 2025 road fuel monitoring report, the Competition and Markets Authority (CMA) found that average supermarket fuel margins had fallen from a high of 10.9p a litre in 2022 to 9.6p in 2025 so far. Non-supermarket margins had risen to 11.1p. The CMA doesn't break Costco out separately, so we can't give its margin. But a 5–7p price gap with the big supermarkets (and about 4p against the cheapest nearby Asda) suggests Costco is taking a noticeably thinner cut, or buying fuel more cheaply, or both. For the background on how this works at Costco worldwide, see why Costco fuel is so cheap.
Does Costco fuel include VAT and fuel duty?
Yes. As at every UK forecourt, the price on the Costco sign includes both fuel duty and 20% VAT.
The DESNZ data for 12 October 2026 lists duty at 52.95p a litre for both petrol and diesel, and VAT at 20%. VAT is charged on top of the duty, so it makes up one-sixth of the pump price. On Costco's 166.58p average that day:
About half of what you pay at Costco is tax. Every forecourt pays the same duty per litre, so Costco only competes on the other half. Its 8.7p gap to the UK average breaks down into about 7.2p less on fuel and margin, plus the VAT on that smaller amount (about 1.5p).
Duty is due to rise when the 5p cut ends on 31 December 2026. The RAC expects 3p a litre on 1 January 2027 and another 2p on 1 March 2027, though the Treasury had not confirmed the staging when we checked. That will raise prices at Costco and everywhere else by the same amount per litre, plus VAT, so it shouldn't change the size of Costco's lead.
If you buy fuel on a Costco Business membership and want to reclaim the VAT, the usual HMRC rules for business fuel apply. They depend on how the vehicle is used, so check with your accountant.
Is Costco fuel better than supermarket fuel?
On price, yes. On quality, there's no evidence either way. Costco UK doesn't publish details of the additives in its fuel, and we found no independent UK tests comparing its petrol or diesel with Tesco, Asda, Sainsbury's or Morrisons fuel. We'd be wary of anyone who claims Costco diesel is better or worse without test data. Our Costco fuel quality post covers the standards, the additives and how it compares with Shell V-Power.
What we can say is that Costco also sells super unleaded, and it's still cheap. On 15 October 2026, our 22 stations averaged 176.3p a litre for super unleaded. That's only about 1p above the government's 12 October average for ordinary unleaded.
How to check today's Costco price before you go
Prices move daily, and the gaps in this post will shift with them. Our UK hub shows today's average and the cheapest Costco, and each station page shows its unleaded, super unleaded and diesel prices with a 30-day chart. For a fair comparison, look at the cheapest supermarket forecourt on your normal route on the same day, not the national average.
