Analysis by the motoring organisation found that unleaded petrol is now 5p per litre more expensive than it was at the start of October, while diesel is 6p more.
RAC Fuel Watch found that petrol went up 2p per litre in January to an average of 139p (136.9p at the start of 2025) and diesel by nearly 3p to 145.7p (from 142.9p).
This means filling up a 55-litre petrol car is more than £2 more expensive than it was four months ago (£76.44 compared to £74.25), and for diesel, it’s over £3 more expensive (£80.15 per tank, compared to £76.70).
The RAC says the rises have been driven by a mid-month spike in the oil price combined with a slight weakening in the value of the pound.
Simon Williams, RAC’s head of policy, said: “It’s not been a good start to 2025 for drivers at the pumps, with prices going up for the fourth month in a row. Sadly, filling up is now nearly £3 more expensive than it was at the start of October.
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“We hope this trend won’t continue and that prices drop back down again. Much, of course, depends on global oil supply and demand.
“While the price of oil can be notoriously volatile, there’s reason to think forecourt fuel prices may get cheaper in the coming months, as some analysts are predicting an average oil price nearer to $70 this year.”
Fuel prices up on supermarket forecourts
RAC Fuel Watch data also showed the average price of a litre of unleaded bought at one of the big four supermarkets rose by 1.6p per litre to 134p and diesel by almost 2p to 141.6p.
Supermarket-bought petrol is currently 3.5p cheaper than the UK average, while diesel is 4p lower.
The average price of petrol at a motorway service station went up by 3.5p in January. Petrol is now 161.9p per litre and diesel is 169.83p if you stop on a motorway.
