Every Driver Pays Up to £4.72 More a Tank by Postcode, AA Finds

• The AA’s analysis of Fuel Finder data puts the gap between the cheapest and dearest region at 8.59p a litre for petrol, worth £4.72 on a 55-litre tank.
• Supermarket forecourts undercut other stations by 2.54p a litre on petrol and 2.93p on diesel, while the AA says price-matching is “holding back lower fuel prices for drivers”.
• Every petrol station must report price changes within 30 minutes, so apps built on the government scheme let drivers check the cheapest pump before they leave the drive.

The Same Tank of Petrol Costs Far More Depending on Where You Fill Up

Two drivers, two identical cars, two full tanks. One pays £4.72 more than the other, and the only difference is the postcode on the forecourt. That is the finding from the AA, which analysed Fuel Finder data published on 8 October and found petrol at 175.91p a litre in the South East against 167.32p in Northern Ireland. Both figures sit around a national average of 174.71p for E10 petrol and 199.88p for diesel.

Edmund King, the AA’s president, summed it up in one line: “Drivers can still face a real postcode lottery at the pumps.” Diesel follows the same script. Scotland was the dearest region at 201.13p a litre and Northern Ireland the cheapest at 193.12p, an 8.01p gap that adds £4.41 to a 55-litre fill.

Stay on the mainland and the gap narrows, but it does not vanish. The AA’s weekly regional table for the week ending 11 October showed Yorkshire and the Humber with the cheapest petrol on the mainland at 173.4p a litre and the South East the dearest at 176.3p. Against the North East the South East premium is 2.7p a litre, which turns a 55-litre tank from £95.48 into £96.97. A van driver filling 80 litres of diesel pays £160.80 in the South East against £159.44 in Yorkshire and the Humber.

Those mainland gaps look small on a single visit. Repeat them and they add up. A driver who fills a 55-litre tank every fortnight and always lands on the £4.72 side of the gap pays about £123 more over a year than a driver who fills at the cheaper end. That is simple arithmetic on the AA’s figures, and it assumes a fortnightly fill, but it shows why a few pence a litre is worth a glance at your phone.

Supermarkets, Motorway Services and the Forecourt Next Door

Region is only part of the story. The AA found a bigger split between types of forecourt. Excluding motorway services, supermarkets sold petrol at an average 172.58p a litre against 175.12p at other stations, a 2.54p difference worth about £1.40 on a tank. On diesel the supermarket average was 197.52p against 200.45p, a 2.93p gap or roughly £1.61 a tank. Supermarkets also cut prices faster after the previous week’s falls.

Even neighbouring garages can sit far apart. On 1 October the AA reported that 2,577 of roughly 8,000 listed stations were charging £2 or more for a litre of diesel, about a third of all sites, and said nearby garages often differ by 6p a litre, with some gaps reaching 10p. On a 50-litre fill a 6p difference is worth £3 and a 10p difference is worth £5.

Why Prices Refuse to Fall at Some Pumps

Wholesale costs tell a different story from the pump. Luke Bosdet, the AA’s fuel expert, said diesel wholesale costs that feed through to the pump “remain at least 4p a litre below where they were in mid September”, yet those potential savings are “barely showing”. His explanation for the regional split is price-matching. He said it is “holding back lower fuel prices for drivers”, and he pointed out that a large number of northern areas have competitive pricing, “much less so in the more populated South East”.

The station-by-station numbers back him up. Over the weekend of 10 and 11 October, 732 petrol stations cut prices and 357 raised them, so twice as many cut as raised, but too few moved to shift the national average. Diesel went the other way. According to the AA’s reading of Fuel Finder data, 823 stations raised diesel prices while 753 cut them. Bosdet said that raises “a big question about the pricing of such an important fuel”.

The wider diesel gap is covered in our earlier report on why diesel now costs more than petrol by 27.6p a litre.

What the Regulator Says and What Fuel Finder Changes

The Competition and Markets Authority (CMA) is watching the same pattern. In its monitoring update of 18 August it said pump prices fell in June as wholesale prices dropped but stayed “significantly above pre-conflict levels”. It found no evidence that retailers actively changed their pricing strategies to take advantage of the crisis. It did say it remained concerned that passive pricing by most retailers is helping sustain high margins, and that some retailers were slow to pass diesel wholesale cuts on to drivers.

Sarah Cardell, the CMA’s chief executive, said: “We know prices at the pump are putting real pressure on drivers’ pockets.” She added that the regulator would “expect any reductions in wholesale prices to be rapidly and fully passed on to drivers”. A more detailed autumn review will examine retailers’ pricing strategies, how quickly wholesale changes reach pump prices, and why prices vary between areas.

Earlier research shows how long the issue has run. In December 2025 the CMA reported that fuel margins remained “persistently high” and said its analysis showed operating costs do not explain them. Average supermarket margins stood at 9.6p a litre for January to September 2025, against 11.1p at non-supermarket retailers, a 1.5p difference. Between November 2024 and October 2025 the average retail spread was 13.9p a litre on petrol and 14.6p on diesel, against 2015 to 2019 averages of 6.5p and 8.6p. Dan Turnbull, the CMA’s senior director of markets, said margins “remain at persistently high levels”.

Fuel Finder is the tool built to make that visible. The Department for Energy Security and Net Zero explains that every petrol filling station must submit its prices “within 30 minutes of any change”, and the data feeds third-party apps and websites. The department names MotorMouth and RAC Fuel Watch among the apps that use it, and estimates an average saving of £40 a year for households that own a car. By the CMA’s August count about 97% of petrol stations are registered, covering an estimated 99% of the fuel sold. From the end of the grace period in April the CMA has sent 1,166 letters and issued compliance notices to 53 sites. No financial penalties have been needed so far.

How to Stop Paying the Postcode Premium

The AA’s advice and the government scheme point the same way. Check a Fuel Finder app before a fill, not at the pump. A 2.5p to 3p saving a litre at a supermarket station adds up to £1.40 to £1.61 a tank on the AA’s figures, and the gap to the dearest garage on a nearby road can reach £3 to £5 on 50 litres.

If a pump price differs from the price shown in an app, the government says drivers can report the mismatch through a government service. That feeds directly into the CMA’s compliance work. The AA’s Lee Morley offered the broader advice: “Drivers can’t control the price at the pump, but there are things they can do to make every drop matter.” He suggested planning routes, combining short trips, avoiding idling and keeping tyres properly inflated.

Driving style makes a difference too. The AA says changing driving style and speed can save up to 15% of fuel, and King’s advice on 1 October was blunt: “The simplest way to cut your fuel bill is to take your foot off the accelerator.”

What Happens Next

Two decisions could move the numbers. The CMA’s autumn review will report on pricing strategies, pass-through and regional differences, and the Budget on 28 October will decide whether fuel duty rises. The AA has called for a fuel duty cut in the Budget. Our guide to what the October 28 Budget could mean for fuel and car tax bills sets out the options.

Until then, the regional gap is the easiest saving to claim. It costs nothing, and the data is already on the phone in the glovebox. Comparing three stations on a map before a fill takes under a minute, and on the AA’s numbers it can be worth up to £4.72 on the tank in front of you.

Sources:

• AA: North v South petrol pump price gap approaches 3p a litre
• AA: Fuel postcode lottery sees drivers pay almost £5 more a tank depending on where they fill up
• AA: Third of diesel forecourts charging two pounds
• GOV.UK: CMA publishes latest monitoring update on road fuel market
• GOV.UK: Enhanced road fuel monitoring report: August 2026
• GOV.UK: Fuel margins remain “persistently high” and this is not explained by operating costs, CMA finds
• GOV.UK: Fuel Finder for drivers: Factsheet