Is it worth driving further for cheaper fuel?
Sometimes. A cheaper station further away saves you money only when the saving on your fill-up is bigger than the cost of the extra fuel you burn driving there and back. For a typical car filling 50 litres, each 1p a litre off the price is worth about 50p, which pays for roughly two extra miles of round trip. A big price gap close by is worth the detour. A small gap a long way off usually isn't.
How do you work out if a cheaper station is worth it?
Add two things together for each station you are thinking about:
- the cost of your fill-up at that station's price
- the cost of the fuel you use driving to the station and back
Whichever station has the lower total is the better deal. The pump price on its own doesn't tell you that, because a station 10 miles away makes you burn fuel to save fuel.
How our "Best value" sort works
When you search by postcode, the Best value sort does this sum for every station on the list. For each one it calculates:
- the pump price multiplied by 50 litres, which is a typical fill-up
- plus the fuel used for the round trip from your search location to the station and back, assuming a car that does about 35 mpg, bought at that station's price
Drive distances come from road routing where it's available, with straight-line distance as a fallback. The station with the lowest total gets the Best value label. It is an estimate. Your own car, your fill size and the traffic on the day will all change the real answer a little.
A worked example
These numbers are made up to show how the sum works. They are not today's prices.
Station A is 2 miles away and sells petrol at 170.0p a litre. Station B is 6 miles away and sells it at 166.0p, which is 4p cheaper. A car doing 35 mpg covers about 7.7 miles on a litre.
| Station A | Station B | |
|---|---|---|
| Pump price (example) | 170.0p | 166.0p |
| 50-litre fill | £85.00 | £83.00 |
| Round trip | 4 miles | 12 miles |
| Fuel used for the trip | 0.52 litres (£0.88) | 1.56 litres (£2.59) |
| Total | £85.88 | £85.59 |
Station B still wins, but only by 29p. The 4p-a-litre saving is worth £2.00 on the fill, and most of it goes on the extra 8 miles of driving. If Station B were a couple of miles further away, Station A would come out ahead.
Is there a simple rule of thumb?
Yes. On a 50-litre fill in a car doing about 35 mpg:
- every 1p a litre you save is worth 50p
- every extra mile of round trip costs a little over 20p when petrol is around 170p a litre
So each 1p a litre saving pays for about two extra miles of round trip, or roughly one extra mile each way. A station 5p cheaper is worth going about 5 miles further out of your way, each way, at most. Beyond that you are breaking even or losing money, before you count your time.
The UK average for petrol is 174.2p a litre right now. The higher prices are, the more each mile of driving costs, but the saving per penny stays the same, so the rule shifts only slightly.
When driving further doesn't pay
- Small top-ups. If you only put in 20 litres, a 4p saving is worth 80p, which covers very little extra driving.
- Thirsty cars. A large SUV or an older car doing 25 mpg uses more fuel getting there, so the break-even distance is shorter.
- Heavy traffic. Stop-start driving uses more fuel than the estimate assumes.
- Your time. Twenty minutes to save 30p is rarely a good trade.
When it does pay
- You're passing anyway. If the cheaper station is on your route to work or the shops, the extra distance is close to zero and you keep the whole saving.
- Big price gaps. The widest gaps are usually between motorway services and ordinary forecourts. In its 2023 market study the CMA found motorway services charged around 20p a litre more for petrol than other stations. See our guide to motorway services fuel prices.
- Larger fills. A 70-litre tank makes each penny saved worth 70p.
Let the finder do the sum
You don't need to do this in your head. Search by postcode and switch to Best value to see which nearby station gives the lowest total once the drive is counted.
Sources
- CMA: plan to help drivers get more competitive fuel prices (2023)
- Live prices: the UK government's Fuel Finder scheme, via Cheapest Fuel. Contains public sector information licensed under the Open Government Licence v3.0.