Pump prices creep back up despite no change in the cost of oil

Despite no real movement in the cost of oil in September, petrol and diesel prices rose by around a penny a litre, data from RAC Fuel Watch data shows.*

The average price of unleaded went up from 134.64p to 135.41p (0.77p) while diesel increased from 142.19p to 143.14p (0.95p) taking a full petrol fill-up to £74 and diesel one to £78.20.

Fuel prices have risen in eight of the past 12 months but are still well below the highs seen in late February. Petrol is 4p below its 12-month peak of 139.65p and diesel is 3p lower than its high of 146.48p – both of which were recorded on 28 February. Fortunately, after these high points prices fell dramatically with both fuels reaching lows on 9 May – petrol bottoming out at 132.03p and diesel at 138.14p.

At the end of September, a litre of petrol bought at one of the four big supermarkets cost drivers 132.11p – 3.3p less than the UK average. Diesel was 139.67p – 3.47p lower than the countrywide average.

The RAC also notes that average retailer margins continue to be high, something which the Competition and Markets Authority referenced in its latest road fuel market report, published last week covering the period from June to August, stating they ‘remain far above historic levels’.

This is highlighted when compared with Northern Ireland where petrol averages 127.8p a litre – 7.6p below the UK average of 135.4p. The diesel comparison is even greater, with a litre 9.4p cheaper than the rest of the UK (133.7p v 143.1p). The RAC estimates average retailer margin in Northern Ireland is currently just 4p per litre, in stark contrast to a UK-wide figure of 11p.

RAC head of policy Simon Williams said: “Sadly, pump prices crept up by a penny a litre in September reversing the drop drivers saw in August. The fact prices have risen at all was made worse by the fact that there was little to no movement in the price of oil, or the pound-to-dollar exchange rate – the prime determiners of fuel prices – and therefore seemingly no justifiable reason for an increase.   

“It was also disappointing to have the Competition and Markets Authority confirm what we have known for some time that retailer margins remain above historic levels. We’re grateful for this level of scrutiny, but it appears yet to have had the effect on retailer behaviour we’d hoped it would. The comparison with average prices and margins in Northern Ireland makes the point that it is possible to sell fuel more cheaply and still make money.

“To get the best value for money wherever drivers are in the UK, we advise shopping around. The best way to do that is by downloading and using the free myRAC app as it makes it easy to find the cheapest fuel. Users can search within five, 10 or 20 miles of their chosen locations which can lead to significant savings.”

The online RAC Fuel Watch resource has more information about the average price of petrol and diesel at the big four supermarkets and at motorway services. It also features graphs showing average prices since 2000.

* UK average pump prices quoted are based on Competition and Markets Authority data from 1-30 September 2025. Wholesale prices from 1-30 September.