Costco petrol stations are consistently among the cheapest forecourts in the UK, often undercutting nearby supermarkets by 5-10p per litre. But to use one, you need a Costco membership costing £42 per year. Whether the fuel savings alone justify that membership fee depends on how close you live to a Costco, how much you drive, and how regularly you can fill up there. Here is the maths.
How much cheaper is Costco fuel?
Costco sources its fuel from established suppliers and sells it at a very small margin, using low fuel prices as a draw to get members through the door. In practice, Costco petrol is typically 5-10p per litre cheaper than nearby branded stations and 3-7p cheaper than nearby supermarket forecourts.
The saving varies by location and by how recently wholesale prices have changed. Costco tends to be slowest to raise prices when wholesale costs increase and quickest to pass on falls, which means the saving is generally most pronounced in periods of rising prices.
The break-even calculation
With a £42 annual membership, you need to save at least £42 in fuel to break even on the membership cost through fuel alone. Here is how many fill-ups that requires at different saving levels:
| Saving vs local alternative | Tank size | Saving per fill-up | Fill-ups to break even |
|---|---|---|---|
| 5p per litre | 55 litres | £2.75 | 16 fill-ups |
| 7p per litre | 55 litres | £3.85 | 11 fill-ups |
| 10p per litre | 55 litres | £5.50 | 8 fill-ups |
If Costco is saving you 7p per litre and you fill up a 55-litre tank, you save £3.85 per fill-up. At that rate, you break even after 11 fill-ups. If you fill up every three weeks, you break even in around 33 weeks — well within the membership year. Everything after that is pure saving.
The distance problem
The key variable most people overlook is the cost of getting to Costco in the first place. If your nearest Costco fuel station is 10 miles away and you have to make a round trip of 20 miles just to fill up, the fuel used for that journey eats into your saving.
In a 38 MPG car, a 20-mile round trip uses approximately 2.4 litres of petrol, costing around £3.74 at 156p per litre. On a 55-litre fill-up saving 7p per litre, you save £3.85 before travel costs — leaving you just 11p better off. At a 5p saving, you would actually lose money on a 20-mile round trip.
Our Worth the Drive Calculator can work this out for any Costco near you. Enter the distance, your MPG and the price difference and it will tell you whether the trip is financially worthwhile.
When Costco fuel is clearly worth it
Costco fuel membership pays off clearly in these situations:
- You live within 5 miles of a Costco fuel station and fill up regularly
- You pass a Costco on your regular commute or route and can fill up without a detour
- You drive high annual mileage (12,000+ miles) and fill up frequently
- You already have a Costco membership for shopping — the fuel saving is then entirely free
When Costco fuel is not worth it
- Your nearest Costco is more than 10 miles away and you would need to make a special trip
- You drive low annual mileage (under 5,000 miles) and fill up infrequently
- Your local supermarket forecourt is already very competitive on price
How to check if Costco fuel is worth it for you
The simplest approach is to compare your nearest Costco price against your usual station using Save at the Pump's live map. Costco stations appear on the map — you can see exactly how much cheaper they are compared to every other station near you and use the Worth the Drive Calculator to account for the distance.
If Costco is showing on our map as significantly cheaper than your usual station and the distance is manageable, the maths usually works out in your favour for regular drivers.